mail/mlmmj: update to 1.8.0

Changelog:

• New 'subrelease' feature: on lists with 'subonlypost', non-subscribers can simultaneously subscribe and release their denied post by replying to a single address. Three variants are provided: subrelease (normal subscription), digestsubrelease, and nomailsubrelease.
• Remove 'selfmoderate' feature, superseded by 'subrelease'.
• Fix thread grouping in digest.
• Fix garbage output in send_digest.
• Properly close SMTP connection on EHLO failure.
• Improve error handling in send_mail.
• Clean up queue file on second do_all_the_voodoo_here failure.
• Use buffered I/O where possible for better performance.
• Update exim4 configuration hints for exim4 >= 4.94.
• Many new unit tests.