mysql_client.c:gw_client_close didn't close client session in cases where session->state == SESSION_STATE_STOPPING. That is a bug and lead to situation where session wasn't closed at all.

Also changed 'authorization failed' to 'access denied'
mysql_common.c: fixed memory leak in gw_receive_backend_auth, and replaced error code '2800' with '28000'.
readconnroute.c:handleError didn't set *succp pointer so uninitialized value was used in caller's context.
makefile.inc: added -lm to linker flags
mysql_backend.c: added a few comments

server/modules/routing/readconnroute.c

@@ -825,7 +825,8 @@ handleError(
 	DCB		*client = NULL;
 	SESSION         *session = backend_dcb->session;
 	client = session->client;
-
+	/** false because connection is not available anymore */
+	*succp = false;
 	ss_dassert(client != NULL);
 }