vdpau: map/unmap surfaces on every cycle, requested by AMD
vdpau: Improve detection of supported files.

A minor improvement on the detection of whether or not a video will
play. It is a good idea to at least make sure that the video codec
is supported and that the resolution does not exceed the supported
resolution.
vdpau: cosmetics
Merge pull request #4294 from FernetMenta/vdpau

vdpau fixes