WINTERMUTE: Add BaseEngine::_workaroundFlags
WINTERMUTE: Pass game flags to BaseEngine::CreateInstance
WINTERMUTE: Add BaseEngine::hasWorkaroundFlag
WINTERMUTE: killAllSounds only if no flag NO_KILLALLSOUNDS

This fixes #6647
WINTERMUTE: Rename wintermute/wintermute_game_flags.h into wintermute/game_flags.h
WINTERMUTE: Rename WintermuteGameFlags -> Wintermute::GameFlags
WINTERMUTE: Rename WINTERMUTE_XXX_FLAG -> WGF_XXX_FLAG