ENH: refs #952. Use InnoDB as engine for password hash table

MyISAM is the default prior to mysql 5.5, and InnoDB is the only one that
guarantees the rows are clustered by primary key

core/database/upgrade/3.2.12.php

@@ -19,7 +19,7 @@ public function mysql()
     $this->db->query("CREATE TABLE `password` (
                         `hash` varchar(128) NOT NULL,
                         PRIMARY KEY (`hash`)
-                     )");
+                     ) ENGINE=InnoDB DEFAULT CHARSET=utf8");
     $this->_movePasswords();
 
     $this->db->query("ALTER TABLE `user` DROP `password`");