Log Message:
Changelog v0.4.19:

* This release adjusts Pigeonhole to several changes in the Dovecot API,
 making it depend on Dovecot v2.2.31. Previous versions of Pigeonhole
 will produce compile warnings with the recent Dovecot releases (but
 still work ok).
- Fixed bug in handling of implicit keep in some cases. Implicit
 side-effects, such as assigned flags, were not always applied
 correctly. This is in essence a very old bug, but it was exposed by
 recent changes.
- include extension: Fixed segfault that (sometimes) occurred when the
 global script location was left unconfigured.