[rbp/omxplayer] Support planar float format audio directly

The update to ffmpeg1.2 has produced a significant performance hit on the Pi when decoding multichannel audio without passthrough.
This is because (most) audio codecs now output planar floating point, rather than interleaved S16 samples.
OpenMax/GPU can handle interleaved S16 samples directly, whereas the floating point planar samples get converted with swr_convert.
This is a slow operation, and a quick profile showed it to be taking about 150MHz of ARM CPU when using 6 channel audio.

I've added support on GPU for a new floating point planar format in audio_decode component.
This PR makes this format also supported for sending audio to the GPU.
The GPU now also handles the 6->8 channel padding so the UpMix() function is no longer required,
which may improve performance compared to pre-ffpeg1.2 version.

This PR requires recent GPU firmware. (384946 or later).
[rbp/omxplayer] Merge with current dvdplayer

To make spotting differences between omxplayer and dvdplayer easier in the future,
this is a pretty slavish copy, including dvdplayer's whitespace and header file includes.
You now get a pretty clean diff between dvdplayer.cpp/dvdplayer.h and omxplayer.cpp/omxplayer.h
[osx] changed, move videoplayer.usevda into darwin_osx.xml and nuke a vda dyload define
Merge pull request #2814 from popcornmix/audio_float_planar

[rbp/omxplayer] Support planar float format audio directly
Also show audio language in the KAI toast when cycling through audio tracks with ACTION_AUDIO_NEXT_LANGUAGE.
Currently only codec/channels are shown.
Merge pull request #2798 from popcornmix/merge_dvdplayer

[rbp/omxplayer] Merge with current dvdplayer
Merge pull request #2781 from mikkle/ShowAudioLanguageInToast

[GUI/Player] Proper audio track lang-name string for kai toast
process border image after base image to ensure it's positioned correctly the first frame the base image is available
changed: allow libname for hidden extension points

needed for repository add-ons
changed: allow calling non-plugin extension points as plugins
added: support python based add-on installers

these are called as a vfs plugin with parameters.
reindent