No real changes, just make wxGridCellEditor accessors const.

IsCreated(), GetControl() and GetCellAttr() should both be const, so make them
so.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73875 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Really fix the problem with caret in wxGrid text editor under MSW.

The problem (see #11681) was due to not allowing the native control handle the
focus loss event. This, in turn, was due to the changes of r58969 which tried
to work around a crash which happened if the grid was destroyed from the code
of one of the user-defined event handlers called during the editor dismissal.

Fix both problems at once by calling event.Skip() in OnKillFocus() to let the
native handler have the event too and postponing the editor dismissal a little
by calling DisableCellEditControl() indirectly from a posted event handler
instead of immediately.

As this reverts the now unnecessary changes of r64646, it closes #15162.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73876 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775