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.
As suggested in #263.
* spot/gen/formulas.cc, spot/gen/formulas.hh, bin/genltl.cc: Implement
these options.
* tests/core/genltl.test: Use them.
* NEWS: Mention them.
* bin/genltl.cc: Change the name and add the bibtex entry.
* bin/man/genltl.x: Replace LNCS by LNAI.
* tests/core/genltl.test: Also test the %F output.
Fixes#80.
* bin/genltl.cc: Add --kr-n2, --kr-nlogn and --kr-n.
* bin/man/genltl.x: Add the paper in the documentation.
* tests/core/genltl.test: Test them.
