Changes 2.5.6:
- Possible to build again with OpenSSL older than version 1.0.1 (was a
  requirement for the previous release due to new protocols TLS 1.1/1.2).
- Support for reading the configuration from the standard input stream.
- New makefile dist target, which can be used to create distribution archives.
Updated mail/imapfilter to 2.5.6