This change slightly improves wxBufferedDC and wxBufferedPaintDC behaviour
when the origin of the DC is shifted, but they still don't work quite right in
this case as they don't use the buffer area of correct size in this case,
which results in cropping the final bitmap (as can be seen in the drawing
sample, which was modified to show wxBufferedPaintDC in action).
Closes#15497.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74951 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
9273033d5a
