New bugzilla keyword

[Elijah P Newren <newren math utah edu>]

The bugsquad has been noticing that a number of bugs had patches ready
to be applied but got blocked by a feature/ui/string/code freeze--and in
some cases, these bugs were forgotten and not noticed again until a freeze
in the following release cycle.  To try to prevent that from occurring
again, a new keyword has been added to bugzilla, BLOCKED_BY_FREEZE.  We
would like to encourage maintainers to add this keyword to the relevant
bugs, and to do a bugzilla query on this keyword after a thaw occurs.

Description of this keyword from
http://bugzilla.gnome.org/describekeywords.cgi:

This keyword should be used for bugs for which action can be taken by the
maintainer once feature/ui/string/code freeze is removed, but for which
all further actions are blocked until that time. Should be reserved for
bugs containing a patch.

Cheers,
Elijah