[mythtv] Heads up, run ./configure for [9915].

[Daniel Kristjansson]

I forgot to mention in the commit log that if you are using XvMC or
OpenGL VSync you need to rerun configure...

XvMC can use now use OpenGL for video display, so there was some overlap
with OpenGL VSync which required new defines.

I don't recommend compiling for XvMC OpenGL video display at the moment
since it slows things down. Also XvMC must be enabled if you compile for
it. I'm working on this in the mythtv-vid tree, so if you want to try it
out there configure with '--enable-xvmc --disable-xvmcw'.

-- Daniel