fixed gcc warnings about not calling base class ctor explicitly in copy ctors (patch 1028986)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@29170 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/bitmap.h

@@ -46,7 +46,7 @@ public:
     wxBitmap() { Init(); }
 
     // Copy constructors
-    wxBitmap(const wxBitmap& bitmap) { Init(); Ref(bitmap); }
+    wxBitmap(const wxBitmap& bitmap) : wxGDIImage(bitmap) { Init(); Ref(bitmap); }
 
     // Initialize with raw data
     wxBitmap(const char bits[], int width, int height, int depth = 1);