[rbp/omxplayer] Fix stall on seek with deinterlace

Need to flush image_fx input port when seeking - this got lost in #3397
[rbp/omxplayer] Add high level locking to OMXVideo

Finally tracked down the long term bug where channel changes sometimes just produce a black screen.
When changing channel we get a couple of open/close cycles as parameters in the hints get updated (e.g. video profile/level)
These are interleaved with decoding of frames from a different thread.
If the components are shut down while a packet is being submitted, we naturally get an OMX error, and playback stalls until another channel change.

OMXAudio already uses a critical section lock. OMXVideo should also do too.
Merge pull request #3443 from popcornmix/seek_deinterlace

[rbp/omxplayer] Fix stall on seek with deinterlace
Merge pull request #3444 from popcornmix/livetv_stall

[rbp/omxplayer] Add high level locking to OMXVideo
[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.

I've also added a small weight to higher multiples of the desired framerate, so if display supports 30, 60 and 120Hz
and the video is 30fps then 30 will now be chosen rather than 120. This reduces the overhead of rendering the gui.
[confluence] Use animated gif as a cheaper working spinner
[rbp/omxplayer] Do we need discontinuity handling?

So far I've not seen what this is needed for and it does cause problems for some files.
h264_parser: Initialize the h264dsp context in the parser as well

Each AVStream struct for an H.264 elementary stream actually has two
copies of the H264DSPContext struct (and in fact all the other members
of H264Context as well):

((H264Context *) ((AVStream *)st)->codec->priv_data)->h264dsp
((H264Context *) ((AVStream *)st)->parser->priv_data)->h264dsp

but only the first of these was actually being initialised. This
prevented the addition of platform-specific implementations of
parser-related functions.

Signed-off-by: Martin Storsjö <martin@martin.st>
h264dsp: Factorize code into a new function, h264_find_start_code_candidate

This performs the start code search which was previously part of
h264_find_frame_end() - the most CPU intensive part of the function.

By itself, this results in a performance regression:
              Before          After
              Mean   StdDev   Mean   StdDev  Change
Overall time  2925.6 26.2     3068.5 31.7    -4.7%

but this can more than be made up for by platform-optimised
implementations of the function.

Signed-off-by: Martin Storsjö <martin@martin.st>
arm: Add assembly version of h264_find_start_code_candidate

               Before          After
               Mean   StdDev   Mean   StdDev  Change
This function   508.8 23.4      185.4  9.0    +174.4%
Overall        3068.5 31.7     2752.1 29.4     +11.5%

In combination with the preceding patch:
                Before          After
                Mean   StdDev   Mean   StdDev  Change
Overall         2925.6 26.2     2752.1 29.4     +6.3%

Signed-off-by: Martin Storsjö <martin@martin.st>
[ffmpeg] Backport of h264_find_start_code_candidate optimisation
[rbp/omxplayer] First attempt at a jpeg thumbnail pipeline
[rbp/omxplayer] First attempt at decode to texture
[rbp/gui] Add switch between higher and lower quality textures

To save memory we default to 16bpp textures,
but provide a GUI option to increase that to 32bpp.
[rbp/gui] Add switch to remove GUI 720p limit
[rbp/omxplayer] Add caching of states to reduce number of round trip delays to GPU
Revert "[rbp/omxplayer] Add caching of states to reduce number of round trip delays to GPU"

This reverts commit 691cfc567895b6645d7052b292f44f557004059b.
 [rbp/omxplayer] Avoid clipping with amplification
[rbp/omxplayer] Add fixed latency mode for live streams