SyncedRingbuffer Cleanup: private fields, clarify reset(boolean)
GLMediaPlayer Multithreaded Decoding: GLMediaPlayer* (Part-4) - WIP

- Use Platform.currentTimeMillis() for accurate timing!

- GLMediaPlayer / GLMediaPlayerImpl
  - Add DEBUG_NATIVE property jogl.debug.GLMediaPlayer.Native
    for verbose impl. messages, i.e. ffmpeg/libav

  - Add 'synchronization' section in GLMediaPlayer API doc (WIP)

  - Use passive non-blocking video synchronization,
    i.e. repeat frames instead of 'sleep'.
    Thx to Xerxes's suggestion.

  - Add flushing of cached decoded frames,
    allowing to remove complicated 'videoSCR_reset_latch'

  - FramePusher (threaded decoding):
    - Always create a shared context!
    - Release context while pausing
    - Pre/post 'getNextTextureImpl()' actions only
      at makeCurrent/release.
    - newFrameAvailable(..) signal after decoded frame is enqueued

- FFMPEGDynamicLibraryBundleInfo
  - Bind add. functions of libavcodec:
    +         "av_init_packet",
    +         "av_new_packet",
    +         "av_destruct_packet",
  - Bind add. functions of libavformat:
    +         "avformat_seek_file",
    +         "av_read_play",
    +         "av_read_pause",
  - DEBUG property := FFMPEGMediaPlayer.DEBUG || DynamicLibraryBundleInfo.DEBUG;

- FFMPEGMediaPlayer
  - Use libavformat's 'av_read_play()' and 'av_read_pause()',
    which may get utilized for network streams, e.g. RTSP

  - getNextTextureImpl(..):
    - Fix retry loop
    - Use postNextTextureImpl/preNextTextureImpl if desired (PSM)

  - Native:
    - Use fixed my_av_q2i32(..) macro (again)
    - Use INVALID_PTS marker (synced w/ Java code)
    - DEBUG: Dump more detailed frame information
    - TODO: Consider passing frame_delay, especially for repeated frames!

- Tests (MovieSimple, MovieCube):
  - Refine KeyEvents control for seek and speed.

- TODO:
  - Proper audio clock calculation - difficult w/ OpenAL !
  - Video / Audio sync:
    - seek !
    - streams w/ very async A/V frames
    - Test Streams:
      - Five-minute-sync-test.mp4
      - Audio-Video-Sync-Test-Calibration-23.98fps-24fps.mp4
      - sound_in_sync_test.mp4
      - big_buck_bunny_1080p_surround.avi