Fixes#297. Implement the following rules.
Fin(i) & Fin(j) by f if i and j are complementary
Fin(i) & Inf(i) by f
Inf(i) | Inf(j) by t if i and j are complementary
Fin(i) | Inf(i) by t.
* spot/twaalgos/cleanacc.cc, spot/twaalgos/cleanacc.hh: Here.
* tests/python/merge.py: Add more test cases.
* NEWS: Mention the change.
Simplify some automata where some marks are identical,
or complementary to another. Fixes #216.
* NEWS: mention the new function.
* spot/twaalgos/cleanacc.cc, spot/twaalgos/cleanacc.hh: Implement
the function.
* tests/Makefile.am, tests/python/merge.py: Test this implementation.
