added new animation mode ".global_anim_sync" for game element graphics

While the existing animation mode ".global_sync" is used to sync game
animations with the frame counter of the game just played, the new
mode ".global_anim_sync" can be used to sync with the global animation
frame counter, which makes it possible to sync with global animations
that are always running during program execution (that is, in the menu
and while playing a game, without interruption).