sql: Add column daemon_flags

We'd like to have a daemon flag, namely "exclusive". This flag should be
published by the daemon into the database, so that is visible to the web
interface.

Although we currently need only a single boolean flag, make it a integer,
so that we can add more flags at a later time without changing the database
scheme.

mysql/create_tables.sql

@@ -165,6 +165,8 @@ CREATE TABLE IF NOT EXISTS mxq_daemon (
     daemon_start    TIMESTAMP   NOT NULL    DEFAULT 0,
     daemon_stop     TIMESTAMP   NOT NULL    DEFAULT 0,
 
+    daemon_flags INT4 NOT NULL DEFAULT 0,
+
     INDEX (daemon_name(64)),
     INDEX (hostname(64))
 );