[dovecot/pigeonhole] ab1f95: Update Dovecot version from v2.2 to v2.4.

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/pigeonhole
  Commit: ab1f9582e20af6567e5d136d8aa846e946e6f21d
      https://github.com/dovecot/pigeonhole/commit/ab1f9582e20af6567e5d136d8aa846e946e6f21d
  Author: Stephan Bosch <stephan.bosch at dovecot.fi>
  Date:   2018-03-05 (Mon, 05 Mar 2018)

  Changed paths:
    M README
    M configure.ac
    M doc/man/doveadm-sieve.1.in
    M doc/man/pigeonhole.7.in
    M doc/man/sieve-dump.1.in
    M doc/man/sieve-filter.1.in
    M doc/man/sieve-test.1.in
    M doc/man/sievec.1.in

  Log Message:
  -----------
  Update Dovecot version from v2.2 to v2.4.