Added a typemap that converts the references returned for some GDI

Added a typemap that converts the references returned for some GDI
objects (Brush, Pen, Font, etc.) into copies, (taking advantage of the
copy-on-write capabilities of the C++ class.)  This is to work around
an issue where getting a GDI object changing it and setting it back to
the DC would trigger an incorrect optimization.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@26044 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775