THREAD segfault

[Bron Gondwana]

On Fri, Jul 22, 2011 at 05:58:07PM +0100, David Carter wrote:
> The attached Berkeley format mailbox contains three messages from
> the imap5 IETF list (including one from Bron!).

Hehe - wow.  There's another open bug about this too.  There seems to
be various brokenness in the THREAD stuff.

#3463

I'm going to merge the two tickets - feel free to add more information
to the end result if you think it will help, but I think the comment
on #2772 is right, we should be normalising the whitespace.

Bron.