It was not covered, probably because it was hard to do something
generic. I choose to duplicate some tests instead, so that things stay
relatively simple.

Minor code cleanup for efficiency, and tests to check the order by clause scrubbing is working correctly and not entering an infinite loop

Fix more occurances of the extending Test bug, "reactivating" a total of 200 tests. SQLAnywhere is missing and is a bit more annyoing to fix, because of a deep inheritance hierachy.

Apperently the doModifyLimitQuery function does not only cover SQL
generated by ORM (Makes sense to use DBAL as seperate component). Therefor
it can happen that a column name does not include the table and so the old
logic was valid anyway. (line 867-869)

Fixed the unit tests to use real column names instead of aliases.

and takes inspiration from this PR https://github.com/doctrine/dbal/pull/374 which was written for this bug http://www.doctrine-project.org/jira/browse/DDC-2622

[DBAL-374] Fix issue with column quoting in primary keys, fixing this in indexes in general is much more complex as the code is messy.

[DBAL-220] Add support for Index flags and implement support for SQL Server CLUSTERED/NONCLUSTERED and MySQL FULLTEXT.