[dovecot/core] cefa6f: pop3-migration: Strip away invalid header lines.

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: cefa6f3df2f30d84f8279109e9152cada9f67e16
      https://github.com/dovecot/core/commit/cefa6f3df2f30d84f8279109e9152cada9f67e16
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2017-09-05 (Tue, 05 Sep 2017)

  Changed paths:
    M src/plugins/pop3-migration/pop3-migration-plugin.c
    M src/plugins/pop3-migration/test-pop3-migration-plugin.c

  Log Message:
  -----------
  pop3-migration: Strip away invalid header lines.

If there's no ":" in the header, remove it. Fixes matching mails with
Zimbra.