Fix wxMSW wxSpinCtrl initial position

wxSpinCtrl created at the given position was always placed at (0, 0) instead
since 05b980aba1 ("Fix wxMSW wxSpinCtrl
appearance: show arrows inside the control").

Fix this in the minimally intrusive way for now by just putting it at the
right position instead of using hard-coded (0, 0) which was done before for
some reason.

See #12297.

src/msw/spinctrl.cpp

@@ -319,7 +319,7 @@ bool wxSpinCtrl::Create(wxWindow *parent,
 
 
     // create the spin button
-    if ( !wxSpinButton::Create(parent, id, wxPoint(0, 0), wxSize(0, 0), style, name) )
+    if ( !wxSpinButton::Create(parent, id, pos, wxSize(0, 0), style, name) )
     {
         return false;
     }