omxil: Include timestamps in the omx debug messages

This is often useful when debugging, when trying to keep track of frames.

Signed-off-by: Martin Storsjö <martin@martin.st>
omxil: Use pts instead of dts by default

I don't know of any codec that actually works better when passed dts
instead of pts. If such codecs exist I do think they're a minority
compared to the ones that can handle both or that do prefer pts.

Additionally, the Android media frameworks pass pts to decoders in
general, not dts. (Vendors might of course have individual hacks,
but this is what the generic code does.)

Signed-off-by: Martin Storsjö <martin@martin.st>