mail/notmuch,mail/notmuch-emacs,mail/py-notmuch: update 0.26.2 -> 0.27

• add LICENSE to pet portlint
• remove BROKEN_powerpc64 since the cause has been fixed in ports r471400
• adjust to upstream's new info page handling
• fix parallel installation of flavored mail/py-notmuch

PR: 229075
Submitted by: Sebastian Schwarz <seschwar@gmail.com> (maintainer)
Relnotes: https://notmuchmail.org/pipermail/notmuch/2018/026684.html