1. minor headers rearrangement: wxprec.h doesn't include setup.h directly

any more, btu defs.h does - and not in the very beginning, but a bit
   later
2. some unused and uncompileable OS2 thing removed from string.cpp


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@3242 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/window.h

@@ -646,7 +646,7 @@ public:
         // get the haqndle of the window for the underlying window system: this
         // is only used for wxWin itself or for user code which wants to call
         // platform-specific APIs
-    virtual WXWidget GetHandle() const;
+    virtual WXWidget GetHandle() const = 0;
 
 protected:
     // the window id - a number which uniquely identifies a window among