Added getCallbacks() methods
Updated SO version for post 3.2 era.
Fixed warning
Updated NEWS from OSG-3.2 branch
Added GL2Extensions::isDrawBuffersSupported() and usage of this in FrameBufferObject.cpp to prevent crash under GLES2 when users attempt to use MRT when it's not supported
Pulled in READE, NEWS and AUTHORS changes from OSG-3.2 branch.
Changed default of serialize draw to off
Merged from OSG-3.2 branch the removal of check for Asio under Windows
Removed trailing spaces
Changed default cull mask to match the left cull mask so that mono rendering of presentations with left/right stereo images/movies works fine.