[rbp/omxplayer] Fix check for contiguous audio buffers

The check for contiguous audio buffers is not sufficient in #3022 causes problems with AAC audio
[rbp/omxplayer] Avoid loss of volume messages

There seems to be a race condition where the volume request arrives as the omx audio pipeline is being created.
Restructure the volume messages to apply the initial volume as pipeline is being created, and add missing locks.
This also reduces the differences between OMXPlayer and DVDPlayer
Merge pull request #3110 from popcornmix/volumeloss

[rbp/omxplayer] Avoid loss of volume messages
Merge pull request #3109 from popcornmix/contiguousaudio

[rbp/omxplayer] Fix check for contiguous audio buffers
[rbp/omxplayer] Handle displaytime more like dvdplayer

We had various glitches when mixing seeking and trickplay with online streams or dvd content.
This tries to match more closely what dvdplayer does and fixes some seek/trickplay jumping issues
Merge pull request #3108 from popcornmix/dvddisplaytime

[rbp/omxplayer] Handle displaytime more like dvdplayer
Use advancedsetting to speed up ReadRate in players