* doc/org/concepts.org, NEWS: Document it.
* spot/twaalgos/determinize.cc, spot/twaalgos/determinize.hh,
spot/twaalgos/sbacc.cc, spot/twaalgos/sbacc.hh: Use it.
* spot/twa/twagraph.cc: Update it on defrag.
* spot/twa/twa.cc (copy_named_properties_of): Copy it.
* tests/python/det.py: New file.
* tests/Makefile.am: Add it.
* python/spot/impl.i (get_original_states, get_original_classes): New
methods, to help with the tests.
