* src/tgbaalgos/safety.hh, src/tgbaalgos/safety.cc: New
files.
* src/tgbaalgos/Makefile.am: Add them.
* src/tgbatests/ltl2tgba.cc: Add option "-O".
* src/tgbaalgos/scc.hh: Update documentation.
* src/tgbatest/Makefile.am (TESTS): Add safety.test.
* src/tgbatest/safety.test: New file.