add ltlsynt executable
For now, ltlsynt only handles LTL realizability. It uses a reduction to parity game followed by Calude et al.'s reduction from parity game to reachability game. * bin/ltlsynt.cc, bin/Makefile.am, bin/man/ltlsynt.x, bin/man/Makefile.am, bin/.gitignore: New binary. * doc/org/arch.tex, doc/Makefile.am, doc/org/tools.org, doc/org/ltlsynt.org: Document it. * spot/misc/game.cc, spot/misc/game.hh, spot/misc/Makefile.am: Parity game wrapper for parity automata + reachability game interface from Calude et al.'s paper.