merge of 5.1-main into 5.1-maria. Myisam->Maria change propagation will follow.

There were so many changes into mtr (this is the new mtr coming) that I rather
copied mtr from 6.0-main here (at least this one knows how to run Maria tests).
I also fixed suite/maria tests to be accepted by the new mtr.

mysys/thr_mutex.c:
  adding DBUG_PRINT here, so that we can locate where the warning is issued.

mysql-test/suite/funcs_1/datadict/is_triggers.inc

@@ -123,6 +123,7 @@ let $my_select = SELECT * FROM information_schema.triggers
 WHERE trigger_name = 'trg1';
 let $my_show =   SHOW TRIGGERS FROM db_datadict;
 --echo # Establish connection testuser1 (user=testuser1)
+let $MASTER_MYSOCK= query_get_value(SHOW VARIABLES LIKE 'socket', Value, 1);
 --replace_result $MASTER_MYPORT MYSQL_PORT $MASTER_MYSOCK MYSQL_SOCK
 connect (testuser1, localhost, testuser1, , db_datadict);
 --replace_result $engine_type <engine_type>