Suggested by František Blahoudek.
* bin/ltlcross.cc: Implement the two options.
* doc/org/ltlcross.org, NEWS: Document them.
* tests/core/complementation.test: Adjust test case.
* tests/core/ltlcross3.test, tests/core/unambig.test: More tests.
* spot/twa/twasafracomplement.cc, spot/twa/twasafracomplement.hh,
tests/core/complementation.cc: Delete.
* tests/Makefile.am, spot/twa/Makefile.am: Adjust.
* tests/core/complementation.test: Rewrite using the new determinization
code.
* python/spot/impl.i: Do not mention twa_safra_complement anymore.
* NEWS: Mention the removal.