security/tor-devel: Update from 0.3.1.5-alpha to 0.3.1.6-rc

[joneum]

Summary

• security/tor-devel: Update from 0.3.1.5-alpha to 0.3.1.6-rc

-Changelog: https://lists.torproject.org/pipermail/tor-talk/2017-September/043518.html

PR: 222071
Reported by: nusenu <[e-mail]>
Submitted by: Yuri Victorovich <[e-mail]> (maintainer)
Approved by: xxx (mentor)
#Differential Revision: https://reviews.freebsd.org/Dxxxxx

Test Plan

~...security/tor-devel: portlint -AC [06:57:19]
WARN: Makefile: you should only use ".if ${PORT_OPTIONS:MDOCS}" to wrap installation of files into /usr/local/share/doc if the collection of files is large and it takes considerable time to copy.
WARN: Makefile: for new port, make $FreeBSD$ tag in comment section empty, to make SVN happy.
WARN: Makefile: "BROKEN_powerpc64" has to appear earlier.
0 fatal errors and 3 warnings found.

poudriere testport:

10.3-amd64
10.3-i386
11.1-amd64
11.1-i386
12.0-CURRENT r323123 amd64
12.0-CURRENT r323123 i386