Import TLS Server Name Indication support patch

Merges Phil Pennock's TLS SNI patch

Closes karelzak/mutt-kz#26

Source: <http://people.spodhuis.org/phil.pennock/software/mutt-patches/>
Merge branch 'sni' of https://github.com/kyrias/mutt-kz

* 'sni' of https://github.com/kyrias/mutt-kz:
  Import TLS Server Name Indication support patch