* src/misc/common.hh (SPOT_RETURN): New macro.
* src/tgba/tgbagraph.hh (out, states, transitions): Use it.

The conversion is not complete, because the conversion from SERE to DRA
used for the closure operator is still building a tgba_explicit_formula.

* src/tgbaalgos/ltl2tgba_fm.cc, src/tgbaalgos/ltl2tgba_fm.hh: Return
a tgba_digraph.
* src/priv/acccompl.cc: Simplify.
* src/graph/ngraph.hh: Add a way to iterate over all names.
* src/tgba/tgbagraph.hh (compute_support_conditions): Return something
useful.  It's actually used by the constructor of testing automata.
* src/tgbatest/wdba.test: Adjust to the fact that state are not
labeled by formulas anymore.
* src/bin/ltl2tgba.cc, src/bin/ltl2tgta.cc: Do not try to enable
UTF8 on automata anymore.

* src/dstarparse/dra2ba.cc: Use tgba_digraph instead of
tgba_explicit_number.
* src/tgbatest/dstar.test: Adjust.

* src/dstarparse/nra2nba.cc: Produce tgba_digraph instead
of tgba_explicit_number.
* src/tgbaalgos/sccinfo.hh (is_useful_state): Make sure
it is reachable.

* src/priv/accmap.hh (acc_mapper_consecutive_int): New class.
* src/dstarparse/nsa2tgba.cc: Build a tgba_digraph, and simplify
using acc_mapper_consecutive_int.

* src/dstarparse/dstarparse.yy, src/dstarparse/public.hh: Adjust the
parser to build a tgba_digraph.
* src/dstarparse/dra2ba.cc, src/dstarparse/nra2nba.cc,
src/dstarparse/nsa2tgba.cc: Temporarily adjust these functions to the
new type until they are rewritten.

* src/neverparse/neverclaimparse.yy, src/neverparse/public.hh,
src/tgbatest/ltl2tgba.cc, src/tgbatest/neverclaimread.test: Adjust.

* src/tgba/tgbagraph.hh: Store the number of the initial state, not a
pointer to it, because if the state vector is reallocated due to some
later calls to new_state(), this pointer will be invalid.
* src/graphtest/tgbagraph.cc, src/graphtest/tgbagraph.test: Test
for this.

* HACKING: Adjust requirements.  g++4.8 is now OK
for all our targets.
* iface/dve2/dve2.cc, src/dstarparse/dstarparse.yy
src/dstarparse/nsa2tgba.cc, src/graph/ngraph.hh,
src/ltlast/atomic_prop.cc, src/ltlast/binop.cc, src/ltlast/bunop.cc,
src/ltlast/multop.cc, src/ltlast/unop.cc, src/ltlvisit/mark.cc,
src/ltlvisit/relabel.cc, src/taalgos/emptinessta.cc,
src/taalgos/tgba2ta.cc, src/tgba/tgbaexplicit.hh, src/tgba/tgbagraph.hh,
src/tgba/tgbasafracomplement.cc, src/tgba/tgbatba.cc,
src/tgbaalgos/cycles.cc, src/tgbaalgos/degen.cc,
src/tgbaalgos/dtbasat.cc, src/tgbaalgos/dtgbasat.cc,
src/tgbaalgos/emptiness.cc, src/tgbaalgos/gtec/gtec.cc,
src/tgbaalgos/ltl2tgba_fm.cc, src/tgbaalgos/magic.cc,
src/tgbaalgos/ndfs_result.hxx, src/tgbaalgos/reachiter.cc,
src/tgbaalgos/scc.cc, src/tgbaalgos/sccfilter.cc, src/tgbaalgos/se05.cc,
src/tgbaalgos/simulation.cc, src/tgbaalgos/tau03.cc,
src/tgbaalgos/tau03opt.cc, src/tgbaalgos/weight.cc: Use emplace()
instead of insert(make_pair(...)) or insert(...::value_type(...)).

These were used in old experiments, but have not turned useful in
practice.  Not worth keeping and maintaining.

* src/tgbaalgos/cutscc.cc, src/tgbaalgos/cutscc.hh: Delete.
* bench/scc-stats/, bench/split-product/: Delete.
* configure.ac, src/tgbaalgos/Makefile.am, README, bench/Makefile.am:
Adjust.

* src/tgba/tgbagraph.hh (new_state, new_states, new_transitions, out,
trans_data): Delegate these useful graph methods so we do not have to
call get_graph().
* src/graphtest/tgbagraph.cc, src/tgbaalgos/dtbasat.cc,
src/tgbaalgos/dtgbasat.cc, src/tgbaalgos/dupexp.cc,
src/tgbaalgos/emptiness.cc, src/tgbaalgos/lbtt.cc,
src/tgbaalgos/powerset.cc, src/tgbaalgos/randomgraph.cc,
src/tgbaalgos/sccfilter.cc,
src/tgbaalgos/sccinfo.cc,src/tgbaalgos/simulation.cc: Simplify.

These were only used by the BDD-based implementation of TGBA, which has
been removed.

* src/tgba/bdddict.cc, src/tgba/bdddict.hh, src/tgba/bddprint.cc: Remove
support for now/next variables.

This translator algorithm is seldom used in practice because we work
with explicit automata everywhere, and this is only useful to build
symbolic automata.  Furthermore, the symbolic automata produced by this
algorithm are larger (when looked at explicitly) than those produced by
ltl2tgba_fm or other explicit translators.

The nice side effect of this removal is that we can also remove a lot of
supporting classes, that were relying a lot on BDDs.

* src/tgba/public.hh, src/tgba/statebdd.cc, src/tgba/statebdd.hh,
src/tgba/succiterconcrete.cc, src/tgba/succiterconcrete.hh,
src/tgba/tgbabddconcrete.cc, src/tgba/tgbabddconcrete.hh,
src/tgba/tgbabddconcretefactory.cc, src/tgba/tgbabddconcretefactory.hh,
src/tgba/tgbabddconcreteproduct.cc, src/tgba/tgbabddconcreteproduct.hh,
src/tgba/tgbabddcoredata.cc, src/tgba/tgbabddcoredata.hh,
src/tgba/tgbabddfactory.hh, src/tgbaalgos/ltl2tgba_lacim.cc,
src/tgbaalgos/ltl2tgba_lacim.hh, src/tgbatest/bddprod.test,
src/tgbatest/mixprod.cc, src/tgbatest/mixprod.test: Delete all these
files.
* bench/ltlcounter/Makefile.am, bench/ltlcounter/README,
bench/ltlcounter/plot.gnu, bench/ltlcounter/run, src/tgba/Makefile.am,
src/tgbaalgos/Makefile.am, src/tgbatest/Makefile.am,
src/tgbatest/cycles.test, src/tgbatest/dupexp.test,
src/tgbatest/emptchk.test, src/tgbatest/ltl2tgba.cc,
src/tgbatest/ltl2tgba.test, src/tgbatest/ltlcross.test,
src/tgbatest/ltlprod.cc, src/tgbatest/spotlbtt.test,
src/tgbatest/wdba.test, src/tgbatest/wdba2.test,
src/tgba/tgbaexplicit.hh, wrap/python/ajax/ltl2tgba.html,
wrap/python/ajax/spot.in, wrap/python/spot.i,
wrap/python/tests/interdep.py, wrap/python/tests/ltl2tgba.py,
wrap/python/tests/ltl2tgba.test: Adjust.

* src/tgbaalgos/powerset.cc, src/tgbaalgos/powerset.hh:
Use tgba_digraph.
* src/tgba/tgbagraph.hh: Improve interface.
* src/tgbaalgos/minimize.cc, src/tgbatest/powerset.cc: Adjust.

This was only used in ELTL stuff, which I just removed because it was
unused.

* src/ltlast/automatop.cc, src/ltlast/automatop.hh,
src/ltlast/formula_tree.cc, src/ltlast/formula_tree.hh,
src/ltlast/nfa.cc, src/ltlast/nfa.hh: Delete.
* src/ltlast/Makefile.am: Adjust.
* src/ltlast/allnodes.hh, src/ltlast/formula.hh, src/ltlast/predecl.hh,
src/ltlast/visitor.hh, src/ltltest/equals.cc, src/ltltest/ltlrel.cc,
src/ltltest/reduc.cc, src/ltlvisit/clone.cc, src/ltlvisit/clone.hh,
src/ltlvisit/dotty.cc, src/ltlvisit/lbt.cc, src/ltlvisit/mark.cc,
src/ltlvisit/postfix.cc, src/ltlvisit/postfix.hh,
src/ltlvisit/relabel.cc, src/ltlvisit/simplify.cc, src/ltlvisit/snf.cc,
src/ltlvisit/tostring.cc, src/tgba/formula2bdd.cc,
src/tgbaalgos/ltl2taa.cc, src/tgbaalgos/ltl2tgba_fm.cc,
src/tgbaalgos/ltl2tgba_lacim.cc, src/tgbatest/ltl2tgba.cc,
iface/dve2/dve2check.cc: Remove all references to automatop.

* src/eltlparse/.gitignore, src/eltlparse/Makefile.am,
src/eltlparse/eltlparse.yy, src/eltlparse/eltlscan.ll,
src/eltlparse/fmterror.cc, src/eltlparse/parsedecl.hh,
src/eltlparse/public.hh, src/eltltest/.gitignore,
src/eltltest/Makefile.am, src/eltltest/acc.cc, src/eltltest/acc.test,
src/eltltest/defs.in, src/eltltest/nfa.cc, src/eltltest/nfa.test,
src/tgbaalgos/eltl2tgba_lacim.cc, src/tgbaalgos/eltl2tgba_lacim.hh,
src/tgbatest/eltl2tgba.test: Delete these files.
* src/Makefile.am, src/tgbaalgos/Makefile.am, src/tgbatest/Makefile.am,
src/tgbatest/ltl2tgba.cc, src/tgbatest/ltlcross.test,
src/tgbatest/spotlbtt.test, README, configure.ac: Adjust.

* src/tgbaalgos/dtbasat.cc, src/tgbaalgos/dtbasat.hh,
src/tgbaalgos/dtgbasat.cc, src/tgbaalgos/dtgbasat.hh: Use tgba_digraph
and modernize syntax slightly.

* src/tgbaalgos/emptiness.cc, src/tgbaalgos/emptiness.hh: Use
tgba_digraph instead of tgba_explicit_string.

* src/priv/accmap.hh (acc_mapper): Rename into...
(acc_mapper_string): ... this, and add
(acc_mapper_int): ... this variant.
* src/tgbaparse/tgbaparse.yy: Adjust to renaming.
* src/tgbaalgos/lbtt.cc: Use acc_mapper_int and build an explicit
automaton.
* src/tgbaalgos/lbtt.hh: Adjust return type.
* src/tgbatest/ltl2tgba.cc: Adjust to new return type.

* src/misc/common.hh (SPOT_UNIMPLEMENTED, SPOT_UNREACHABLE,
SPOT_UNREACHABLE_BUILTIN): New macros.
* src/bin/dstar2tgba.cc, src/bin/ltlcross.cc,
src/dstarparse/dstar2tgba.cc, src/eltlparse/eltlparse.yy,
src/ltlast/binop.cc, src/ltlast/bunop.cc, src/ltlast/constant.cc,
src/ltlast/formula_tree.cc, src/ltlast/multop.cc, src/ltlast/nfa.cc,
src/ltlast/unop.cc, src/ltlvisit/dotty.cc, src/ltlvisit/lbt.cc,
src/ltlvisit/lunabbrev.cc, src/ltlvisit/mark.cc,
src/ltlvisit/randomltl.cc, src/ltlvisit/simpfg.cc,
src/ltlvisit/simplify.cc, src/ltlvisit/snf.cc, src/ltlvisit/tostring.cc,
src/misc/intvcomp.cc, src/misc/minato.cc, src/tgba/bdddict.cc,
src/tgba/formula2bdd.cc, src/tgba/tgbasafracomplement.cc,
src/tgbaalgos/eltl2tgba_lacim.cc, src/tgbaalgos/ltl2taa.cc,
src/tgbaalgos/ltl2tgba_fm.cc, src/tgbaalgos/ltl2tgba_lacim.cc,
src/tgbaalgos/simulation.cc, src/tgbatest/ltl2tgba.cc:  Use them.
* src/sanity/style.test: Catch assert(0) and assert(!"text");

* src/graph/graph.hh (new_states): Call reserve().
* src/tgbaalgos/randomgraph.cc: Use tgba_digraph
instead of tgba_string_explicit.

* src/tgbaparse/parsedecl.hh, src/tgbaparse/public.hh,
src/tgbaparse/tgbaparse.yy: Adjust to return a tgba_digraph.
* src/priv/accmap.hh: New file to help creating acceptance
conditions from strings.
* src/priv/Makefile.am: Add accmap.hh
* src/tgba/tgbagraph.hh (tgba_digraph::named_t): New typedef.
* wrap/python/spot.i: Declare that tgba_digraph inherits from tgba.
* src/tgbatest/complementation.cc, src/tgbatest/explpro2.test,
src/tgbatest/explpro3.test, src/tgbatest/explpro4.test,
src/tgbatest/explprod.cc, src/tgbatest/explprod.test,
src/tgbatest/ltl2tgba.cc, src/tgbatest/maskacc.cc,
src/tgbatest/maskacc.test, src/tgbatest/mixprod.cc,
src/tgbatest/powerset.cc, src/tgbatest/randtgba.test,
src/tgbatest/readsave.test, src/tgbatest/tgbaread.cc,
src/tgbatest/tgbaread.test, src/tgbatest/tripprod.cc,
src/tgbatest/tripprod.test: Adjust to the change.

* src/ltlenv/declenv.cc, src/ltlenv/declenv.hh,
src/ltlenv/defaultenv.cc, src/ltlenv/defaultenv.hh,
src/ltlenv/environment.hh, src/tgbaalgos/compsusp.cc: Declare name as
const.

* src/bdd.h, src/cppext.cxx: Handle bddtrue and bddfalse using
special types.

* src/tgbaalgos/dtgbasat.cc, src/tgbaalgos/eltl2tgba_lacim.cc,
src/tgbaalgos/simulation.cc, src/tgbaalgos/tau03opt.cc: Fix
cases where bddtrue and bddfalse where used in a ternary operator.
* src/sanity/style.test: Allow bdd_true()/bdd_false() to be
used in ternary operators.

* src/tgbaalgos/sccinfo.cc, src/tgbaalgos/sccinfo.hh: Implement
the acc_filter_simplify filter, and generalize composition to
be n-ary.
* src/tgbaalgos/sccfilter.cc (used_acc): New method.

The new version currently supports removal of useless state as well as
removal of acceptance sets from non-accepting SCCs (the two versions).
It does not yet support simplifation of acceptance sets and removal of
suspendable formulae.  However the design, using filters that are
composed before being applied, should make it easier to implement.

* src/tgbaalgos/sccfilter.cc, src/tgbaalgos/sccfilter.hh: Implement
the new scc_filter and supporting classes.
* src/tgbaalgos/simulation.cc, src/tgbaalgos/simulation.hh: Use it.
The simulation now always return a tgba_digraph.
* src/tgbatest/sim.test: Adjust.

* src/tgbaalgos/simulation.cc: Buid a tgba_digraph as the result of the
simulation.
* src/tgba/tgbagraph.hh (create_namer): New function.
* src/tgbatest/basimul.test: Add an additional test case that caused a
bug fixed in a previous patch.
* src/tgbatest/sim.test: Adjust.