libtwolame MP2 encoding support

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
mp2: match twolame default options
lavu: Add packed YVYU422 pixel format
swscale: support converting YVYU422 pixel format
rawvideo: Support decoding YVYU422 FourCC
fate: update tests for YVYU422 pixel format
doc: Change the multitable rendering in texi2pod

Makes it working better for our documentation purposes.
doc: Use a 3 columns multitable

Make the html output much nicer.
doc: Completely document the x264 options

And fix an option mismatch.