Put audio output into a worker thread.
Handle unused variable warnings
Windows audio fix
Fix beep API and unconnected slot
Enable Qt multimedia
Move Windows sound API to right thread context and make it an object member. Perform init within the right thread context. Add capability to play .wav files in addition via QMultiMedia
Improve audio output logic and consistency
Make Windows playback synchronous so that audio does not overlap
Make eSpeak on Linux synchronous
Revert "Make eSpeak on Linux synchronous"

This reverts commit 4d033715a8748a2bfdd0c0698d69cbf5eba4260a.
espeak: use AUDIO_OUTPUT_SYNCH_PLAYBACK
Move audio file to resource
Merge branch 'audio_thread' of github.com:mavlink/qgroundcontrol into audio_thread
Disable tunes, allow to re-enable them with a simple define
Move init to correct thread
More rigor in thread tear down
Merge branch 'audio_thread' of github.com:mavlink/qgroundcontrol into audio_thread
Merged master
Merge pull request #1082 from mavlink/audio_thread

Put audio output into a worker thread.