This improves the determinism in a few cases.
* spot/twa/twagraph.cc (merge_edges): Encapsulate the two
passes into lambdas so that they are very easy to swap.
* spot/twa/twagraph.hh (merge_edges): Adjust documentation.
* tests/python/mergedge.py: Add test case.
* tests/core/alternating.test, tests/python/alternation.ipynb:
Determinism was improved.
* tests/core/parity2.test, tests/core/readsave.test,
tests/core/sbacc.test, tests/python/_product_susp.ipynb,
tests/python/atva16-fig2a.ipynb, tests/python/decompose.ipynb,
tests/python/highlighting.ipynb, tests/python/satmin.ipynb,
tests/python/simstate.py: Adjust expected order of edges.
* NEWS: Mention the change.
* 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.
