Add a property to select YUV colorspace. Currently implemented only in
vo_vdpau and vo_xv. Allows switching between BT.601, BT.709 and
SMPTE-240M (vdpau only).
The xv support uses the "XV_ITURBT_709" attribute. At least my NVIDIA
card supports that; I don't know whether other xv implementations do.
Bind the colorspace switch to the 'c' key by default. 'c' is currently
used by vo_sdl for some fullscreen mode change thing, but at the moment
that does not conflict and if it will in the future then vo_sdl can
change.
VDPAU part based on a patch from Lauri Mylläri <[email protected]>