2. Fix for full cell background to be painted. (One line on the edges
was showing through to the background.)
3. Added current cell highlight. Currently it just draws a thick
border using the gridLineColour just inside the cell borders.
4. Make dragging a little less sensitive by ensuring that the mouse
drags at least 3 pixels before anything is done to the grid.
5. CaptureMouse while drag-selecting cells and fixed to make cells
visible if dragging outside window boundaries. Still a problem here
though, it moves way to fast to see what's happening (at least on MSW.)
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@6002 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
07296f0b12