GLMixer Code

linking with lib pthread (ignore if not found) for cases when libav are
compiled with pthread (ideal solution would be to test, but doesn't
really matter..)

Changed default layout to stack Mixing, layout and current source
toolboxes (reported issue for low resolution screens).

Updated download to GLMixer 1.4 r941

Improved packaging NSIS for windows, including companion programs.
Disabled SPOUT compilation for now.

Bug fix in setting of fullscreen monitor index

Implementation of aspect ratio resizing buttons in the Layout toolbox.

Fix user preference and settings.

Added Preference option for View Context Menu on background : selection
of Zoom menu or Cursor menu.
Bug fix Tablet support.

Tablet support : Emulation of Extra mouse button for Eraser of tablet.

Implementation of pressure sensitive parameter of the cursors (allowing
it) with QTabletEvent.