Fixes#282.
* spot/misc/bddlt.hh (bdd_less_than_stable): New function.
* spot/twa/twagraph.cc (merge_edges): Use it.
* tests/core/genltl.test: Adjust, and add an extra test
for the behavior of #282.
* tests/core/complement.test, tests/core/degenid.test,
tests/core/ltldo.test, tests/core/prodor.test,
tests/core/readsave.test, tests/core/sbacc.test,
tests/python/atva16-fig2a.ipynb, tests/python/automata.ipynb,
tests/python/decompose.ipynb, tests/python/dualize.py,
tests/python/highlighting.ipynb, tests/python/piperead.ipynb,
tests/python/product.ipynb, tests/python/simstate.py,
tests/python/tra2tba.py: Adjust all expected outputs.
* NEWS: Mention the bug.
Operator &= used to always move Fin to the front, it does not anymore.
The only thing it does now is to merge Inf(x)&Inf(y) as Inf({x,y}).
Operator |= is now symmetrical and merges Fin()s.
Fixes#253.
* spot/twa/acc.cc, spot/twa/acc.hh: Simplify &= and make |= symmetrical.
* spot/twaalgos/cleanacc.cc: Fix conjunction order.
* tests/core/acc.test, tests/core/acc2.test, tests/core/parseaut.test,
tests/core/readsave.test, tests/core/satmin2.test,
tests/core/sccdot.test, tests/python/acc_cond.ipynb,
tests/python/accparse.ipynb, tests/python/automata.ipynb,
tests/python/product.ipynb, tests/python/randaut.ipynb: Adjust test
cases.
For #212.
* spot/twa/twa.hh: Rename prop_deterministic() as prop_universal(),
and keep the old name as deprecated.
* spot/twaalgos/isdet.cc, spot/twaalgos/isdet.hh: Rename
is_deterministic() as is_universal(), and add a new function
for is_deterministic().
* doc/org/concepts.org, doc/org/hoa.org, doc/org/tut21.org,
spot/tl/hierarchy.cc, spot/twa/twagraph.cc,
spot/twaalgos/are_isomorphic.cc, spot/twaalgos/determinize.cc,
spot/twaalgos/dtbasat.cc, spot/twaalgos/dtwasat.cc,
spot/twaalgos/hoa.cc, spot/twaalgos/minimize.cc,
spot/twaalgos/postproc.cc, spot/twaalgos/product.cc,
spot/twaalgos/randomgraph.cc, spot/twaalgos/remfin.cc,
spot/twaalgos/simulation.cc, spot/twaalgos/totgba.cc,
spot/twaalgos/word.cc, tests/python/product.ipynb,
tests/python/remfin.py: Adjust.
* NEWS: Mention the change.
