No changes, just extract wxCreateHiddenWindow() declaration in a header.

Add wx/msw/private/hiddenwin.h with wxCreateHiddenWindow() declaration instead
of declaring it manually in all the files using it.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69170 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/utilsexc.cpp

@@ -82,9 +82,7 @@
     #include "wx/dde.h"         // for WX_DDE hack in wxExecute
 #endif // wxUSE_IPC
 
-// implemented in utils.cpp
-extern "C" WXDLLIMPEXP_BASE HWND
-wxCreateHiddenWindow(LPCTSTR *pclassname, LPCTSTR classname, WNDPROC wndproc);
+#include "wx/msw/private/hiddenwin.h"
 
 // ----------------------------------------------------------------------------
 // constants