fix build of iax-mutex.c

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@5146 d0543943-73ff-0310-b7d9-9358b9ac24b2

libs/iax/src/iax-mutex.c

@@ -17,7 +17,8 @@
  *
  */
 
-
+#define _XOPEN_SOURCE 600
+#include <stdlib.h>
 #include "iax-mutex.h"
 
 
@@ -29,7 +30,7 @@ struct mutex {
 };
 
 #else
-#define _XOPEN_SOURCE 600
+
 #include <pthread.h>
 struct mutex {
 	pthread_mutex_t mutex;