adapting to new inheritance of wxMemoryDC (under MSW only at the moment)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@43110 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dcgraph.h

@@ -36,6 +36,9 @@ class WXDLLEXPORT wxGCDC:
 
 public:
     wxGCDC(const wxWindowDC& dc);
+#ifdef __WXMSW__
+    wxGCDC( const wxMemoryDC& dc);
+#endif    
     wxGCDC();
     virtual ~wxGCDC();