Compilation fix for gcc-4 and newer.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@56456 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/os2/frame.h

@@ -215,6 +215,8 @@ private:
     DECLARE_DYNAMIC_CLASS(wxFrame)
 };
 
+MRESULT EXPENTRY wxFrameWndProc(HWND  hWnd,ULONG ulMsg, MPARAM wParam, MPARAM lParam);
+MRESULT EXPENTRY wxFrameMainWndProc(HWND  hWnd,ULONG ulMsg, MPARAM wParam, MPARAM lParam);
 #endif
     // _WX_FRAME_H_