Log Message:
mail/dovecot2-pigeonhole: update to 0.5.15

Security release.

v0.5.15 2021-06-21  Aki Tuomi <aki.tuomi@open-xchange.com>

* CVE-2020-28200: Sieve interpreter is not protected against abusive
  scripts that claim excessive resource usage. Fixed by limiting the
  user CPU time per single script execution and cumulatively over
  several script runs within a configurable timeout period. Sufficiently
  large CPU time usage is summed in the Sieve script binary and execution
  is blocked when the sum exceeds the limit within that time. The block
  is lifted when the script is updated after the resource usage times out.
* Disconnection log messages are now more standardized across services.
  They also always now start with "Disconnected" prefix.
- managesieve: Commands pipelined together with and just after the
  authenticate command cause these commands to be executed twice.