[dovecot/core] 2b2f0d: configure: Switched version number to 2.4.devel

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: 2b2f0de75ee7cd7b2ed0a05f02a60b6c8eda8e68
      https://github.com/dovecot/core/commit/2b2f0de75ee7cd7b2ed0a05f02a60b6c8eda8e68
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2017-12-15 (Fri, 15 Dec 2017)

  Changed paths:
    M configure.ac

  Log Message:
  -----------
  configure: Switched version number to 2.4.devel