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.
Also disable i18n because that seems to be causing many problem to Mac
users building Spot for git and not knowing how to install
Locale::gettext.
* tools/help2man: Update from upstream, plus the two changes from
2b4cf8e7cb and
f7b65001e9.
* bin/man/Makefile.am: Remove the -L flag.
