[feature request] PauseBg / StopBGAnim state controller

[F0b1aZ]

Actually we have Pause and Superpause states controllers, and both allow to pause the background among with characters setting pausebg = 1. Since it works only if at least one character is paused, it should be useful to have an indipendent controller which freezes background only, ot at least freezes all stage animations.

Thanks!