Log Message:
Update net/couriertcpd to 0.57.1.  Changes from version 0.56.0 include:

* Avoid hardcoding file descriptor numbers where possible.

* Include remote port number in IMAP and POP3 logs.

* Ignore SIGPIPE errors in couriertcpd, preventing couriertcpd from being
  terminated if the stderr logger crashes.

* Looping SPF query should abort with SPF UNKNOWN, as per specs.

* "SSL23" tries SSLv3 before falling back to SSLv2.

* Prime the OpenSSL entropy pool on platforms that don't have a ready
  source available.