Add the deadlock note to ast_spawn_extension as well

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@164422 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/pbx.h

@@ -492,6 +492,10 @@ int ast_extension_close(const char *pattern, const char *data, int needmore);
  *
  * This adds a new extension to the asterisk extension list.
  *
+ * \note It is possible for autoservice to be started and stopped on c during this
+ * function call, it is important that c is not locked prior to calling this. Otherwise
+ * a deadlock may occur
+ *
  * \retval 0 on success 
  * \retval -1 on failure.
  */