Merge pull request #2537 from popcornmix/mediatime

[rbp] Set mediatime on GPU after a seek.
upnp: container updates weren't propagating to GUI for current path
[rbp] Add reporting of fifo fullness for use with hdmi_status_show in debug builds
[rbp] Move m_messenger.Init from constructor to OnStartup

This makes omxplayer constistent with dvdplayer.
It avoids an initial stray message to immediately try and go normal speed when it should be buffering.
[rbp] Expose GetAudioRenderingLatency

This could be useful for detecting underrun conditions
[rbp] Add OMXLateCount to query if packets have arrived late

Could be useful for detecting underrun conditions
[rbp] Add more debug logging
[rbp] Use CurrentHostCounter consistently
[rbp] Use correct size when determining fifo has space in it

This can cause player to get a decode error from audio_decode component
closing stream when packet doesn't actually fit.
[rbp] Always acquire lock when using OMXMediaTime

I don't believe the lock=false call should ever be done unless caller already has lock
[rbp] Cosmetics
[rbp] The stillframe logic doesn't work on Pi and causes stuttering
[rbp] Avoid coming out of stalled state due to uninitialised variable

m_endtime is only initialised when we underrun. Use m_av_clock->OMXAudioBuffer() to protect access to uninitialised variable.