[rbp/omxplayer] Use an omx decode to texture pipeline

This PR uses an openmax pipeline to handle jpeg decode/resize/convert to texture without the decoded pixels being returned to the arm.

The jpeg is decoded in stripes which saves memory. There is no need for the RGBA32 pixel buffer to ever exist on the arm.
It is straightforward to choose whether the textures are 16bpp or 32bpp which could be a useful option on 256M Pi.

This scheme is *much* faster, and is the main factor in the recent raspberry-pi "speed" video.
It is well tested and openelec and raspbmc builds have been made with this patch in.