acc: recognize parity acceptance
It has two modes: strict or not. In strict mode (tested in hoaparse.test), the acceptance formula has to match exactly the one given in the HOA spec. In non-strict mode (tested in accparse2.py) any equivalent formula is accepted. * src/twa/acc.cc, src/twa/acc.hh (acc_cond::is_parity): New method. * src/twaalgos/hoa.cc: Use it. * src/tests/hoaparse.test: Test it. * wrap/python/spot_impl.i: Bind it. * wrap/python/tests/accparse2.py: New file. * wrap/python/tests/Makefile.am: Add it.