[Dovecot] Manual thread breaking from Thunderbird

[rosenfield.albert at gmail.com]

> No idea. Would be at least useful to have a standard to base it on. Of
> course no-one prevents you from coding it sooner. :)

Gonna be tough to squeeze in between all the updates that needs to be
done to the MUA.  Hopefully it doesn't take more than 5 minutes to set
up a Thunderbird build environment.

..... Mu-ha-ha...