This function changes the parity acceptance of an automaton.

* spot/twaalgos/parity.cc, spot/twaalgos/parity.hh: Here
* python/spot/impl.i: Add spot/twaalgos/parity.hh
* spot/twaalgos/Makefile.am: Add spot/twaalgos/parity.{cc,hh}
* tests/core/parity.cc, tests/core/parity.test: Add
spot::change_parity() tests
* tests/python/parity.ipynb: Add documentation about
spot::change_parity()
* tests/Makefile.am: Add tests/core/parity.{cc,hh} and
tests/python/parity.ipynb
* doc/org/tut.org: Add the html page of tests/python/parity.ipynb