keyword cleanup

[Luis Villa <luis villa gmail com>]

I'd like to nuke some keywords in the ongoing quest to keep things 'clean'.

* PATCH: we have good patch editing by now. I'm not entirely sure of the
status of querying for these, though, so perhaps we need to fix that
before we remove PATCH altogether.
* BLOCKED_BY_FREEZE: same as above, though we should flame the list
about open BLOCKED_BY_FREEZE bugs before deleting it and losing the
information.
* 1.x-parity: I don't think we care about GNOME 1.x parity anymore.
* DOCS_NEEDED: evidence suggests this is not used ATM.
* PATCH_NEEDED: patches are always needed. I hate this keyword. :)
* HELPWANTED: doesn't make much sense to me, but appears to be more
widely used- perhaps someone should review the open ones to see how they
are used in the wild?
* screenshot: do we care? why do we need this information?
* ximian: hasn't been used in ages.

Would love to hear feedback, thanks-

Luis (trying to get back in the game; goal is to read all 2.9/2.10 bugs today)