7.9.1

1. Fix - colz handling on THStack, avoid multiple palette drawings
2. Fix - bug in pad.Divide context menu command
3. Fix - drag and drop of histograms on empty sub-pads
4. Fix - add missing colors 100 - 127
5. Fix - correct online context menu for histogram title
6. Fix - copy all X axis attributes in multi-graph painter
7. Fix - if histogram WebGL drawing fails, fallback to default 2D