[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.
[omxplayer] When in dual audio mode, make one output the slave

Helps audio sync between the two outputs.
Previously both sinks sent competing adjustments to clock
[omxplayer] Fix for aspect ratio of portrait videos

Follows same logic as dvdplayer with GL ES renderer.
[omxplayer] Ignore occasionally valid pts values

They cause live tv stutter.
[omx] Skip the resize when not needed when decoding jpegs

The decode to texture path almost always uses cached jpegs that are the correct size, so the resize is rarely needed.
The re-enc path usually needs resizing, but may not where the source is small.

Skipping the resize stage saves a little time and memory on GPU and also saves some setup time.
[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
libcec: Make verbose logging optional
Merge pull request #4703 from popcornmix/stereoview

[omxplayer] Support stereo view modes with scaling
Merge pull request #4710 from popcornmix/framerateswitch

[omxplayer] Support hdmi framerate changes during video
Merge pull request #4708 from popcornmix/tvstutter

[omxplayer] Ignore occasionally valid pts values
Merge pull request #4706 from popcornmix/portrait_aspect

[omxplayer] Fix for aspect ratio of portrait videos
Merge pull request #4705 from popcornmix/dualslave

[omxplayer] When in dual audio mode, make one output the slave
Merge pull request #4709 from popcornmix/skipresize

[omx] Skip the resize when not needed when decoding jpegs
Merge pull request #4746 from popcornmix/ceclog

libcec: Make verbose logging optional
videoplayer: adapt lateness detection and dropping to buffering
video player: present correct pts to user for a/v sync (after buffering in renderer)
videoplayer: some rework and documentation
renderer: bump buffers to 5