fix build

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@6727 d0543943-73ff-0310-b7d9-9358b9ac24b2

libs/sofia-sip/libsofia-sip-ua/su/su_global_log.c

@@ -47,7 +47,9 @@
  * 
  * @sa <sofia-sip/su_debug.h>, su_log_global
  */
+#ifdef DOXYGEN
 extern char const SU_DEBUG[];
+#endif
 
 #ifdef SU_DEBUG
 #define SU_DEBUG_ SU_DEBUG