omxil: Switch to the alternative OMX ABI, used on the raspberry pi

This breaks usage of the omxil decoder with any other OMX core - this
cannot easily be switched at runtime since it affects how structs
are laid out.
omxil: Try to load the broadcom host library and IL core

Don't unload the library though. On init, it starts background
threads, which keep running even after the library is deinitialized.
Therefore, this library cannot be unloaded after being loaded and
initialized.
omxil: Hardcode the fact that the OMX.broadcom.video_decode supports the role video_decoder.avc
omxil: Change the signalled OMX version to 1.1.2

The broadcom OMX IL core requires this in order to respond to
requests.

This shouldn't probably break other OMX cores, unless they are
picky about it in the same way, requiring version 1.1.1.
omxil: Use larger input buffers to the decoder

The default ones on the raspberry pi aren't large enough for higher
resolution content.