Remove unneeded or outdated _MSC_VER macro #ifs
[rbp/omxplayer] Simplify clock handling

In OMXClock we have an almost complete copy of DVDClock, so just use DVDClock directly.

The passing through of CDVDClock functions from OMXClock is hopefully temporary,
as I think clock manipulation is better handled from OMXPlayer than audio/video players.
[rbp/omxplayer] Add plumbing for audio GetCacheTotal
[rbp/omxplayer] OMX spec says we can transition from execute to idle
[rbp/omxplayer] We don't require this for command line omxplayer
[rbp/omxplayer] Add calls for stepping and retreiving the clock adjustment
[rbp/omxplayer] Use OMXPlaySpeed for pause/resume
[rbp/omxplayer] dispmanx now handles negative rectangles correctly so adjustment not required