[rbp] Hardware accelerated resampling

This replaces the format conversion, up/down mixing and resampling code from ActiveAE with a GPU accelerated version.
Should significantly reduce CPU when using paplayer or dvdplayer.

Requires updated firmware
[PiResample] Work around AE not providing correct src_bits
[ffmpeg] Speed up wtv index creation

The index creation is O(N^2) with number of entries (typically thousands).
On a Pi this can take more than 60 seconds to execute for a recording of a few hours.

By replacing with an O(N) loop, this takes virtually zero time
[rbp/omxplayer] When opening a stream don't try to update gui so often
[omxcodec] Clamp video texture at edges to avoid image wrapping
[PiSink] Remove unneeded header and use CAEChannelInfo directly
[omxplayer] Remove PCMRemap and handle multichannel mixing like ActiveAE does
[omxplayer] Fix for 3d video in mono mode

The test for no aspect wasn't correct, causing large black bars
[omxplayer] Remove unused framerate functions
[omxplayer] Make the sharpness control act as a sharpness control.

This fixes scaling kernel as Mitchell Netravali, and varies sharpness over range B=[5/3,0] C=[-1/3,1/2]
[rpi] Include ntsc frequencies in list of supported resolutions
[omxplayer] Allow a framerate callback from GPU to trigger a hdmi mode change
[omxplayer] Request to be notified about framerate changes
[omxplayer] Don't propagate 3d flags based on supported 3d modes
[omxplayer] Support stereo view modes with scaling

The Pi only supported a single view rectangle, which is sufficient for all mono view modes,
but only supports a subset of stereo modes.

To work around this, the scaling rectangles were ignored in 3D modes and 3D video was treated as unscaled.
While this worked or square pixel, 16:9 content on a 16:9 display, it went wrong is various other conditions.

@sraue reported that mono view of SBS/TAB content wasn't scaled correctly, and other forum reports
aspect ratio errors in widescreen 3D videos.

As it wasn't trivial to work around these bug reports, I've added a new stereo flags to the firmware
that allows a second display region to be created for the second eye, allowing scaling to work.

I've been through the video stereo modes (none, sbs, tab) and the display stereo modes (mono, sbs, tab)
and all the zoom modes, and compared the scaling to xbmc on windows and all seem to match

Requires udpated firmware.
[graphics] Don't set stereo mode based on resolution

The resolution change should follow stereo mode
[graphics] Allow switching to a more suitable 3D resolution
[3D] Support switching to 3D resolutions

Include matching 3D flags (SBS/TAB) in the score of a resolution to switch to, to enable switching to 3d modes.
Also remove the old code that treated 3D modes differently when assigning a score.
[graphics] Make pixel ratio for 3d modes consistent

Note: Use the stored stereo flags from lists of resolutions.
Use current stereo mode for current resolution.
[PiSink] More attempts to reduce underrun audio glitches with multichannl and high samplerate