[mythtv] bug in edit cutpoints when XvMC_VLD defined

[Simon Kenyon]

i have an Epia M-9000 and i find that if i enable XvMC_VLD and i try to edit a 
recording to insert cutpoints, then when i'm down at single frame or single 
keyframe, only one frame in four is displayed.

i have to go forward four times and then the picture jumps forward four 
frames.

if i turn off XvMC_VLD then i can move forward/backward a single frame -
but normal play is awful (as you might expect)

i also noticed that if i turned on XvMC on the user interface (but did not 
compile it in) then myth crashes when trying o play something. should the 
checkbox be visible if XvMC is not compiled in?

regards
--
simon