[mythtv] New configure script automatically enabling XVMC

[Dave Meador]

I use a EPIA M1000 with a HDTV screen.  Unfortunately the onboard Via
unichrome video drivers do not support (to my knowledge, please correct me
if I am wrong) 1920x1080i or 1280x720 video modes.  I was very dismayed by
this, so to get high quality video added a PCI/NVIDIA-GeForce5700FX to the
second slot.  This works very well and all desired modes are supported.  I
then disable the onboard VIA video.

Unfortunately... in this instance automatically selecting XvMC-VLD for
EPIA-x000's will break my setup which uses a NVidia video card.

$0.02  ;-)

> XvMC is still experimental. The reason I made XvMC-VLD default on is
> because you always want that on when compiling for the EPIA M-x000's.
> But my assumption that the presence of libviaXvMC indicated that you
> were compiling for a EPIA M-x000 is no longer correct.
> 
> -- Daniel