GLMixer Code

Fixed various problems in Video File: improper test of alpha channel,
wrong display of buffer BPP, and support for files encoded with wrong
width (maintaining performance otherwise).

Cleanup optimization of rendering pipeline.

Removed unused dependency on libavfilter-dev

Fixed support for (bad) videos with unusual frame size.

Disable transparency for displaying source in catalog.

Bugs fix for Recorder : FFVHUFF format recording in single threaded,
MPEG warning on Frame size, Non-monotonic PTS warning, pause/resume
timing, and RenderingManager PBO initialization.

Cleanup implementation of PBO for RECORDER.

Fix bugs in management of FBO in Sources.

Use of Pixel Buffer Objects for improving RECORDING.

Do not require xsltproc for compilation (it is useful only for linux
package generation)