Merge pull request #29 from j-b-m/master

This fixes framebuffer producer that was corrupted when encountering an invalid frame
Add new count producer
Add mlt_service_move_filter() and Mlt::Service::move_filter().
Fire service-changed event in mlt_service_move_filter().
Misc YAML fixes
Set interim version 0.8.9.
Add alpha channel support to avformat consumer.

This requires that you set the pix_fmt property correctly for the codec:
  vcodec=png pix_fmt=rgba
  vcodec=targa pix_fmt=bgra
  vcodec=qtrle pix_fmt=argb

Sometimes you also need to use mlt_image_format=rgb24a to prevent losing
the alpha channel during image processing.
Fix test frame image crashing GLSL.

Using mlt_frame_get_image() on error affects image stack, add image
conversion when using test_card_producer.
Rename this to self in consumer sdl.
Rename this to self in sdl_preview consumer.
Make mlt_consumer_purge() more thorough. (SF-187)

This is applied to SDL consumers only at the moment since that is what
most applications are using. Needs to be extended to other consumers.
Fix regression rewind or fast forward playback stalling.
Fix crash purging closed queue.
Fix race condition in mlt_consumer_stop().
Cleanup and improve frame rate selection.
Cleanup and improve aspect ratio selection.

The overrides for DV are not necessary since we dropped support for
FFmpeg v0.5 and 0.6. FFmpeg uses our values since Sept. 2010.

Muxer's aspect ratio is generally preferred over the codec's if it is
sane. See FFmpeg doxygen comments for av_guess_sample_aspect_ratio().
Implement mlt_consumer.purge in rtaudio consumer.
Implement mlt_consumer.purge in multi consumer.
Improve pause in melt.
Fix compile errors on ffmpeg v0.7 - 0.11.