DRM framework support:

- add a sniffer for DRM files
- add DRMSource and DRMExtractor for es_based DRM
- add pread in FileSource.cpp for container_based DRM
- add native DRM framework API calls in the player for
  DRM audio/video playback

Change-Id: I4b9ef19165c9b4f44ff40eeededb9a665e78a90f