implement is_safety_mwdba().
Note: I swapped the name of safety and guarantee when I
implemented is_safety_automaton() on 2010-03-20. Fortunately,
is_safety_automaton() was only used where is_guarantee_automaton()
would have been correct.
* src/tgbaalgos/safety.cc (is_guarantee_automaton): Rename as ...
(is_guarantee_automaton): ... this.
(is_safety_mwdba): New function.
* src/tgbaalgos/safety.hh: Adjust and add documentation.
* src/tgbaalgos/minimize.cc: Use is_guarantee_automaton() instead
of is_safety_automaton().
* src/tgbatests/safety.test: Rename as ...
* src/tgbatests/obligation.test: ... this, and augment the
test.
* src/tgbatest/Makefile.am: Adjust.
* src/tgbatest/ltl2tgba.cc (-O): Display whether a formula
represent a safety, guarantee, or obligation property.
* NEWS: Adjust.
