Added wxDC::CreateGraphicsContext and implemented it for a few DCs

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@53344 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/dcclient.h

@@ -28,6 +28,10 @@ public:
 
     virtual ~wxWindowDCImpl();
 
+#if wxUSE_GRAPHICS_CONTEXT
+    virtual wxGraphicsContext* CreateGraphicsContext();
+#endif
+
     virtual bool CanDrawBitmap() const { return true; }
     virtual bool CanGetTextExtent() const { return true; }