Committed MainFrame.cxx/.h with a fix for the problem of segmentation faults
while updating online histograms.  The problem was the pointers to the
histograms needed to be changed in the TGLVContainers when the histograms
were deleted and recreated due to being updated.  The main difficulty was
getting a handle on which TGLVEntry matched which histogram, when the
histogram pointers were obtained from the TPad and not the TGLVContainer. 
Anyway, you can now view online histograms without the program crashing.