* src/tgbaalgos/degen.cc, src/tgbaalgos/degen.hh: New argument
to disable the "jump to the accepting level if the entering
state as an accepting self-loop" optimization.
* src/tgbaalgos/postproc.cc, src/tgbaalgos/postproc.hh: Check
the degen-lowinit option and pass it on to degeneralize().
* src/bin/spot-x.cc: Document it.
* src/tgbatest/degenlskip.test: Add some tests.
* src/tgbatest/ltl2ta.test: Update value.  We output less
accepting states now.