Avoid redefine error.

--- Python-3.1/Modules/main.c.orig	2009-02-12 09:55:38.000000000 -0600
+++ Python-3.1/Modules/main.c	2009-07-22 22:50:19.981100800 -0500
@@ -14,9 +14,11 @@
 #include <windows.h>
 #ifdef HAVE_FCNTL_H
 #include <fcntl.h>
+#ifndef PATH_MAX
 #define PATH_MAX MAXPATHLEN
 #endif
 #endif
+#endif
 
 #ifdef _MSC_VER
 #include <crtdbg.h>