mail/msmtp: update to 1.8.0
- Add MSMTPD option that install minimal SMTP server called msmtpd that listens on the local host and pipes mails to msmtp (or another program); enabled by default,
- Upstream switched from libidn to libidn2, update dependency accordingly,
- Enable GNUTLS by default instead of OPENSSL as per upstream recommendation [1].