auditing obfsproxy

Hi,

At the request of asn, I started to audit obfsproxy - I started and have been making some commits as I go along:

Here's my gcc/ld hardening one trick pony: https://gitweb.torproject.org/user/ioerror/obfsproxy.git/commit/b3367507b465703762c0c6dd9816f9eef133c350

A basic start at an apparmor profile: https://gitweb.torproject.org/user/ioerror/obfsproxy.git/commit/d1599cf358bb2471014b1aaaed2b10fe22516bc2

Spec notes: https://gitweb.torproject.org/user/ioerror/obfsproxy.git/commit/4d0405a6269f3abf0bb862e9e0a7587cbe5fbeef

Threat model notes: https://gitweb.torproject.org/user/ioerror/obfsproxy.git/commit/053b267d96053624daa326d3ad6171dd3763b498

Here's the full branch: https://gitweb.torproject.org/user/ioerror/obfsproxy.git/shortlog/refs/heads/compile_hardening