res_config_mysql.c: Support hostnames up to 255 bytes.

Fixes #654

(cherry picked from commit 18ed610d4e)

addons/res_config_mysql.c

@@ -84,7 +84,7 @@ struct mysql_conn {
 	AST_RWLIST_ENTRY(mysql_conn) list;
 	ast_mutex_t	lock;
 	MYSQL       handle;
-	char        host[50];
+	char        host[MAXHOSTNAMELEN];
 	char        name[50];
 	char        user[50];
 	char        pass[50];