* spot/twaalgos/translate.cc, spot/twaalgos/translate.hh: Build
automata with generic acceptance by doing product of automata for
smaller subformulas.
* bin/spot-x.cc: Mention ltl-split.
* NEWS: Mention the change, and show some results.
* tests/core/genltl.test, tests/python/_product_susp.ipynb,
tests/python/highlighting.ipynb: Adjust test cases.
* doc/org/ltl2tgba.org: Update.
* tests/core/gragsa.test: Add another formula to cover more
code.

* spot/twaalgos/product.cc, spot/twaalgos/product.hh: Implement it.
* tests/python/_product_susp.ipynb: New file.
* tests/Makefile.am: Add it.
* NEWS: Mention it.

* .dir-locals.el: Here

* spot/twaalgos/aiger.cc: here
* tests/core/ltlsynt.test: add a non-regression test

Zielonka algorithm used to iterate over an std::unordered_set, thus
producing different strategies depending on compiler...

* spot/misc/game.cc: replace std::unordered_set with std::set

* .dir-locals.el: fix typo for indent-tabs-mode

closes #355

* doc/org/citing.org, bin/man/ltlsynt.x: add SYNT2018 paper
* doc/org/ltlsynt.org: fix documentation

Related to issue #351.

* spot/twaalgos/sccfilter.cc: When handling weak automata, we know
they are very-weak if the SCC count is equal to the number of states.
* tests/core/dca2.test, tests/core/monitor.test,
tests/core/parity2.test, tests/core/randomize.test,
tests/core/readsave.test, tests/core/remfin.test,
tests/core/sccsimpl.test, tests/core/wdba2.test,
tests/python/dualize.py, tests/python/remfin.py: Adjust output.

... instead of inherently-weak.  The reason they were tagged
as inherently-weak is historical: this property was introduced
1.5 years before the weak propery.

Fixes #351.

* spot/twaalgos/ltl2tgba_fm.cc: Use prop_weak() instead of
prop_inherently_weak().  Also be more conservative about the use of
single_acc when unambiguous automata are generated.

Part of issue #351.

* spot/twaalgos/sccfilter.cc, spot/twaalgos/sccfilter.hh: Specialize
for inherently-weak automata.
* spot/twaalgos/postproc.cc: Simplify.
* tests/core/dca2.test, tests/core/parity2.test,
tests/core/prodor.test, tests/core/randomize.test,
tests/python/automata.ipynb, tests/python/highlighting.ipynb,
tests/python/product.ipynb, tests/python/remfin.py,
tests/python/stutter-inv.ipynb: Adjust.
* NEWS: Mention it.

* spot/gen/formulas.cc, spot/gen/formulas.hh: Here.
* bin/genltl.cc: Add options.
* tests/core/genltl.test: Test them.
* NEWS: Mention them.

This improves gf_guarantee_to_ba() on formulas GF(φ) where the
automaton for F(φ) as several leading transiant SCCs.  E.g.,
GF(a <-> XXXa) where we know get results that are as good as
those of delag without loosing on the cases where delag's technique
would actually produce two big automata.

* spot/twaalgos/gfguarantee.cc: Implement this.
* spot/twaalgos/gfguarantee.hh, NEWS: Document it.
* tests/core/ltl2tgba2.test, tests/core/ltl3ba.test: Add test cases.

Fixes #347.

* spot/twaalgos/minimize.cc, spot/twaalgos/minimize.hh: An SCC of the
determinized automaton is marked as accepting if it intersects any
accepting SCC of the original automaton.  This can be checked by
making a product.  As a consequence the output of minimize_wdba() now
always includes the original language, and minimize_obligation() only
needs a single containment check.
* NEWS: Mention this.

Fixes #354.

* spot/tl/simplify.cc: Implement the rules.
* doc/tl/tl.tex, NEWS: Document them.
* tests/core/reduccmp.test: Add tests.
* tests/core/det.test, tests/core/satmin.test: Adjust.

* bin/genltl.cc, spot/gen/formulas.cc, tests/core/genltl.test: Adjust.
* NEWS: Mention it.

Fixes #352.

* bin/autfilt.cc: Add the options.
* tests/core/alternating.test: Test them.
* NEWS: Mention them.

Together with the previous patch, this Fixes #353.

Implementing this required to extend our interface two support
two-parameter patterns.

* spot/gen/formulas.cc, spot/gen/formulas.hh: Implement it.
* bin/genltl.cc: Add --sejk-f.
* bin/common_output.cc, bin/common_output.hh: Adjust to handle
"line numbers" that are not integers (e.g., "3,2"), since those
are used to display pattern parameters.
* bin/ltlfilt.cc: Adjust.
* python/spot/gen.i: Add support for two-parameters patterns.
* tests/core/genltl.test, tests/python/gen.ipynb: Augment.
* NEWS: Mention it.

These correspond to the first three blocks of table 1 in S. Sickert,
J. Esparza, S. Jaax, and J. Křetínský: Limit-Deterministic Büchi
Automata for Linear Temporal Logic.  CAV'16.  LNCS 9780.

For #353.

* spot/gen/formulas.cc, spot/gen/formulas.hh, bin/genltl.cc: Implement
the new families.
* tests/core/genltl.test: Test it.
* bin/man/genltl.x, NEWS: Document it.

When dealternating the VWAA for GFa, our result had two states that
could not be fused by simulation because of unmatched acceptance mark.
With this change, the result can be simplified.

* spot/twaalgos/alternation.cc: Here.
* tests/core/alternating.test, tests/python/alternation.ipynb: Update
test case.
* NEWS: Mention it.

* spot/misc/bitset.cc, spot/misc/bitset.hh (set, clear):
Turn asserts into exceptions.
* spot/twa/acc.hh (mark_t): As a consequence, the
constructor is not noexcept anymore.
* tests/core/acc.cc, tests/python/except.py: More tests.

* spot/twaalgos/alternation.cc: Always call ensure_weak_scc().

The exception raised by << and >> when shifting mark_t by too many
bits are only enabled in SPOT_DEBUG, as those operations are quite
low-level.  However we were always testing them, and although we
wanted them to be active in Python, it was not always the case.

* spot/twa/acc.hh: introduce max_accsets() as
a static constexpr method, so we can see it in Python.
* spot/misc/bitset.hh: Fix preprocessing directive
so the check is actually enabled when compiling the Python
bindings.
* bin/autcross.cc, bin/autfilt.cc, bin/ltlcross.cc: Use max_accsets().
* tests/core/acc.cc: Comment out the shifting exception when
SPOT_DEBUG is unset.
* tests/python/except.py: Make sure the exception is always raised in
Python.

* spot/twa/acc.hh, spot/twaalgos/alternation.cc,
  spot/twaalgos/determinize.cc, spot/twaalgos/ndfs_result.hxx,
  spot/twaalgos/tau03.cc, spot/ltsmin/ltsmin.cc, tests/core/parity.cc:
  here

* spot/twaalgos/split.cc: split_2step relies less on bdd, which improves
  its performance
* tests/python/split.py: update test

* spot/twa/twagraph.hh, spot/twa/twagraph.cc: here
* NEWS: document it
* tests/core/twagraph.cc, tests/core/tgbagraph.test: test it

* spot/misc/bitset.hh: add methods set() and clear()
* spot/twa/acc.hh: deprecate comparison of mark_t with unsigned, and
  rely more on biset for efficiency

* README, doc/org/hoa.org: Here.

* NEWS, bin/autcross.cc, bin/autfilt.cc, bin/ltlcross.cc,
configure.ac, spot/parseaut/parseaut.yy, spot/twa/acc.cc,
spot/twa/acc.hh, tests/core/acc.cc, .gitlab-ci.yml: Here.

* spot/misc/bitset.hh: Here.
* spot/misc/bitset.cc: New file.
* spot/misc/Makefile.am: Add it.
* spot/twa/acc.hh: Conditionally remove the exception checks around
shift operators.
* spot/misc/common.hh (SPOT_ASSUME): New macro.

* spot/misc/common.hh (SPOT_BUILTIN_UNREACHABLE): Typo.

Fixes #348, reported by Jeroen Meijer.

* bin/autfilt.cc: If -B is used with many --product,
degeneralize intermediate products as needed.
* NEWS: Mention the change.
* tests/core/prodchain.test: New file.
* tests/Makefile.am: Add it.
* spot/twa/acc.cc, spot/twa/acc.hh: Fix reporting of
overflow.
* tests/core/acc.cc: Adjust.

Fixes #350.

* spot/twaalgos/product.cc: Implement this change.
* NEWS, spot/twaalgos/product.hh: Mention it.
* spot/twa/acc.cc, spot/twa/acc.hh (acc_cond::sat_mark): New method.
* tests/python/_product_weak.ipynb: New file.
* tests/Makefile.am: Add it.
* tests/python/automata.ipynb, tests/python/highlighting.ipynb,
tests/python/product.ipynb, tests/core/prodor.test: Adjust test cases.

* tests/core/ltlsynt.test: here

* tests/core/genltl.test: here
* spot/gen/formulas.cc: typo

* tests/core/ltlfilt.test: here