* src/tgbaalgos/isweakscc.cc, src/tgbaalgos/isweakscc.hh: Do not pass
automata since they are known from the scc.  Avoid several dynamic
casts.  Try to match the established vocabulary wrt "weak" and
"inherently weak".  The old is_weak_scc() that used to enumerate cycles
is therefore renamed to is_inherently_weak_scc(), while the new
is_weak_scc() will should ensure all transitions are fully accepting.
* NEWS: Mention the new interface.