doctrine/dbal — pull request #294 by deeky666 (2013-03-28 20:17:20+00:00)
Title: Allow removing column comment on some platforms

Some platforms currently do not remove a comment on a column on table alteration.
This PR fixes this. Also updated platform and functional schema tests for this.
Besides that OraclePlatform now does not generate a useless ALTER TABLE MODIFY SQL snippet when only the column comment has changed, as this is handled seperately through COMMENT ON COLUMN SQL statement.