MAINT-1147 Fix for frame stall on region crossing.

indra/llrender/llimagegl.cpp

indra/llrender/llrendertarget.cpp

indra/llrender/llrendertarget.h

indra/newview/lldrawable.cpp

indra/newview/lldrawpool.cpp

indra/newview/lldrawpool.h

indra/newview/lldrawpoolterrain.cpp

indra/newview/lldrawpoolterrain.h

indra/newview/lldrawpooltree.cpp

indra/newview/llspatialpartition.cpp

indra/newview/llsurface.cpp

indra/newview/llsurfacepatch.cpp

indra/newview/llviewerdisplay.cpp

indra/newview/llviewermessage.cpp

indra/newview/llviewerobjectlist.cpp

indra/newview/llviewerregion.cpp

indra/newview/llviewerwindow.cpp

indra/newview/llvoavatar.cpp

indra/newview/llvotree.cpp

indra/newview/llworld.cpp