* spot/twaalgos/game.cc, spot/twaalgos/game.hh (game_info): Move...
* spot/twaalgos/synthesis.cc,
spot/twaalgos/synthesis.hh (synthesis_info): ... here, because this
structure contains only synthesis stuff. Also rename "solver" to
"algo" to match the ltlsynt option.
(solve_game): Move the two argument version of this function here,
since that's the only game-related generic function that use
synthesis_info.
* bin/ltlsynt.cc, tests/core/ltlsynt.test, tests/python/games.ipynb,
tests/python/synthesis.py, NEWS: Adjust all uses and mentions.