For queries that list all errors of a certain type.
This patch needs to be applied manually, update.php won't work.
Change-Id: I42abded9df3ef2ff242be2b16f4c57bafc03ae39
linter_cat is now an int ID that points to a row in the new
lint_categories table.
The mapping between category names and ids is all handled in PHP, and
cached in APC.
Note that you will need to drop the `linter` table manually and re-run
update.php for this to take effect.
Change-Id: I369d9b4d8d08289b4a20d1cd29a2e327bad28ef8
