(Port to 2.8) Fix for wxMemoryDC::GetAsBitmap(wxRect) on Windows.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@48236 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/bitmap.h

@@ -105,6 +105,10 @@ public:
     // get the given part of bitmap
     wxBitmap GetSubBitmap( const wxRect& rect ) const;
 
+    // NB: This should not be called from user code. It is for wx internal
+    // use only. 
+    wxBitmap GetSubBitmapOfHDC( const wxRect& rect, WXHDC hdc ) const;
+
     // copies the contents and mask of the given (colour) icon to the bitmap
     bool CopyFromIcon(const wxIcon& icon);