Handle libvlc_MediaPlayerCorked / libvlc_MediaPlayerUncorked events
Increment a pause_counter when corked, decrement it when uncorked.
When the pause_counter is set from 0 to 1: Pause the playback (and any service that need to be paused).
When the pause_counter is set from 1 to 0: Resume the playback.
This will be used by the chromecast module to notify that the user paused/resumed it from an outside apps.