dbsake sieve + --master-data is broken on mariadb10

[abg]

This probably also affects mysql 5.6 when gtids are used. On MariaDB when --master-data is used, a new section is included:

--
-- GTID to start replication from
--

-- SET GLOBAL gtid_slave_pos='0-1-36509';

This confuses sieve's naive tokenizer / parser which aborts on a silly error like:

# ./dbsake sieve < all_databases.sql.gz > /dev/null
Unable to determine section type at line 25: -- GTID to start replication from

Ultimately the tokenizer needs to be made more robust - similar to issue #69 where this causes issues with compact or other "non-standard" mysqldump formats.