GLMixer Code

CMake for FreeFrameFFPlay plugin (was missing).

Fixed implementation for insertion of source (problem with previous
commit).

BUGFix: resolved the issue of "Not enough space to insert the source
into the stack" when creating large number of sources (e.g. drop files).
Now a depth is correctly computed for a new source when hitting the
MAX_DEPTH_LAYER, and if necessary all sources are re-distributed
uniformly on the depth axis to make room for new sources.

Fixed implementation of SVG source. Incrementation of XML file version to
1.2.

Implementation of a busy mode for GLMixer for informing user during
(long) loading or saving activities.

Project for new Plugin with FFPlay code (to play a video with audio)

Added scaling parameter for FreeFrameQtScreenCapture.

Threaded implementation of GLM session saving.

BugFix ScreenCapture plugin under OSX

OSX fix correction.