Allow copy of a single cell demarcated by the grid cursor.
Paste of lib_table s-expressions should always start at 0,0.
Let caller or specialized sub-class do auto-sizing; don’t
do it from within the base GRID_TRICKS.
Don’t start GRID_TRICKS menu IDs at -1; wxWidgets doesn’t
like it when you get to 0.
Add column visibility menu.
(cherry picked from commit e5071ed)
Jeff Young