[dovecot/core] b2fa20: configure: Link libsmtp before libdns

[GitHub]

  Branch: refs/heads/master-2.2
  Home:   https://github.com/dovecot/core
  Commit: b2fa20bf11aa1e3dd06ed5c839f5b0e93e429a7e
      https://github.com/dovecot/core/commit/b2fa20bf11aa1e3dd06ed5c839f5b0e93e429a7e
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2017-01-10 (Tue, 10 Jan 2017)

  Changed paths:
    M configure.ac

  Log Message:
  -----------
  configure: Link libsmtp before libdns

Fixes linking LIBDOVECOT when using .a libraries