wxDisplay cleanup/rewrite:

- wxDisplay is now a concrete class and uses a pImpl-based design
- got rid of four duplicate but subtly different versions of trivial
  single display-only wxDisplay implementation (but 2 versions of Mac
  Classic and Mac CoreGraphics implementations each still remain...)
- assorted code simplifications and memory leaks fixes


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38127 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/os2/chkconf.h

@@ -21,6 +21,11 @@
    to disable here features not supported currently or enable
    features required */
 
+#if wxUSE_DISPLAY
+#   undef wxUSE_DISPLAY
+#   define wxUSE_DISPLAY 0
+#endif /* wxUSE_DISPLAY */
+
 #if wxUSE_STACKWALKER
 #   undef wxUSE_STACKWALKER
 #   define wxUSE_STACKWALKER 0