[tor-relays] Port for obfsproxy

[Zack Weinberg]

Oh, and, the cryptographic choices made in the ST paper are, in
retrospect, quite poor: for instance, I had no idea when I picked it
that AES-GCM was so troublesome in software, and all of the elliptic
curve stuff has since been obsoleted by Elligator.

Anyone interested in hacking on steganographic transports nowadays
would be well-advised to begin from something else, such as Yawning
Angel's LODP.