* src/bin/autfilt.cc: Use isomorphism_checker.
* src/tgbaalgos/are_isomorphic.cc, src/tgbaalgos/are_isomorphic.hh: Wrap
are_isomorphic inside a class to keep the canonic version of the first
automaton between two calls, and use a more efficient algorithm in case
both automata are deterministic.
* src/tgbatest/isomorph.test: Add tests for deterministic automata.