[MPlayer-dev-eng] Better pause

[Uoti Urpala]

I wrote an improved pause implementation that allows executing keyboard
and slave commands without unpausing. It's in the "pause" branch in git.
It's not quite complete yet but I think it's already usable.

The implementation uses some VO support. Currently it works best with VO
xv or gl. Other VOs will step a frame forward when updating OSD
contents. correct-pts needs to be active or video contents may not be
updated when seeking while paused. You may get some alsa error messages
caused by pause - audio reset at seek - unpause (but that doesn't seem
to affect usability otherwise).