* python/spot/impl.i: Add bindings for tra2tba
* spot/twaalgos/Makefile.am: Record tra2tba.cc, tra2tba.hh
* spot/twaalgos/tra2tba.cc: Implement transformation of TRA to TBA
* spot/twaalgos/tra2tba.hh: Introduce declaration of tra_to_tba
* tests/Makefile.am: Record tra2tba tests
* tests/core/tra2tba.cc: Add driver for tests
* tests/core/tra2tba.test: Add tests of tra2tba transformation
