Fixes #55.

* src/tgba/acc.hh: Do not store a bdd_dict_ptr, it is not used.
* src/tgba/tgba.hh, src/tgba/tgba.cc, src/ta/ta.hh,
src/tgba/tgbagraph.hh, src/tgbaalgos/dtgbasat.cc,
src/tgbatest/acc.cc: Adjust.