Applied patches by Scott Pleiter:

Applied patches by Scott Pleiter:

[ 643866 ] small wxGrid API changes

adds GetValue to the gridcelleditors to facilitate
querying values from the editors, also changes several
methods to virtuals to simplify inheritance.

[ 643867 ] wxGrid cell LNF & behaviour patch

Enables the grid to render its cells grey when the grid
control is disabled. Also fixes several problems when
making the gridcelleditors visible. Improves the layout
of multi-line row/column labels. Changes the CellEditor
show from a MOUSE_DOWN to a MOUSE_UP, this
stops the editor starting when creating a selection
beginging in the currently selected cell.

[ 643868 ] wxGrid rendering tweaks, improves look.

Draw the row/column using system colours. Change the
default wxGrid settings to have a more neutral starting
point - grey lines, non-bold label font, black/white
selection etc.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@18148 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775