Excessive repainting with tables

[Dekel Tsur]

I've found out that when one inserts/deletes a char in a table, the cells in
the table are redrawn 3 times !

This happens as BufferView::updateInset is called 3 times:

InsetText::LocalDispatch
 |
 +--->InsetText::UpdateLocal
       |
       +--->BufferView::updateInset
              |
              +--->InsetTabular::UpdateInsetInInset
                    |
                    +--->InsetTabular::UpdateLocal
                          |
                          +--->BufferView::updateInset

InsetTabular::LocalDispatch
 |
 +--->InsetTabular::UpdateLocal
       |
       +--->BufferView::updateInset

Obviously, this should be fixed...