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

src/common/string.cpp

@@ -13,12 +13,6 @@
   #pragma implementation "string.h"
 #endif
 
-#ifdef __WXPM__
-#define LINKAGECPP _Optlink
-#else
-#define LINKAGECPP
-#endif
-
 /*
  * About ref counting:
  *  1) all empty strings use g_strEmpty, nRefs = -1 (set in Init())