[dvdplayer] Make players pointers rather than objects
[dvdplayer] Move Step in PlayerVideo
[dvdplayer] Make methods protected
[dvdplayer] Remove unused functions
[dvdplayer] constify functions
[dvdplayer] Create a base class for audio and video players
[omx] Make method const where possible
[omxplayer] Remove unused WaitCompletion function
[players] Add and const-ify GetDynamicRangeAmplification
[players] Add and const-ify IsEOS
[omxplayer] const-ify BadState and GetAudioRenderingLatency
[dvdplayer] Add dummy hooks in useful places
[omxplayer] Make OpenStream protected
[omplayer] Add Step function
[omxplayer] const-ify
[omxplayer] Make omxplayer use dvdplayer as base class