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/timer.cpp

@@ -31,6 +31,7 @@
 #endif
 
 #include "wx/msw/private.h"
+#include "wx/msw/private/hiddenwin.h"
 
 // ----------------------------------------------------------------------------
 // private globals
@@ -76,11 +77,6 @@ UINT_PTR GetNewTimerId(wxMSWTimerImpl *t)
 LRESULT APIENTRY _EXPORT wxTimerWndProc(HWND hWnd, UINT message,
                                         WPARAM wParam, LPARAM lParam);
 
-// implemented in utils.cpp
-extern "C" WXDLLIMPEXP_BASE HWND
-wxCreateHiddenWindow(LPCTSTR *pclassname, LPCTSTR classname, WNDPROC wndproc);
-
-
 // ----------------------------------------------------------------------------
 // wxTimerHiddenWindowModule: used to manage the hidden window used for
 // catching timer messages (we need a module to ensure that the window is