pyconfig.h must be included before any system header (as per Python docs; essential for Python 2.3 under Tru64 Unix)

[SVN r17799]

test/docstring.cpp

@@ -3,13 +3,13 @@
 // copyright notice appears in all copies. This software is provided
 // "as is" without express or implied warranty, and with no claim as
 // to its suitability for any purpose.
-#include <string>
 #include <boost/python/operators.hpp>
 #include <boost/python/class.hpp>
 #include <boost/python/module.hpp>
 #include <boost/python/def.hpp>
 #include <boost/python/scope.hpp>
 #include <boost/python/manage_new_object.hpp>
+#include <string>
 #include "test_class.hpp"
 
 // Just use math.h here; trying to use std::pow() causes too much