Make vaapi decoder compatible with latest libva changes
Modify vaapi decoder to choose the format used by vaapi.
This avoids possible double format conversions if the output or encoder expects a diffrent format.
Add vaapi h264 encoder
Disable DRM for now
Use fast cached SSE4.1 copying for vaapi-enc
Win32: use Wide Chars APIs
libmp4: rewind stream before falling back to avformat

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
Preparations for VPP