Add pure-hack targets

[fredemmott]

Some candidates:

• https://github.com/facebook/fbctf
• https://github.com/hhvm/user-documentation

[justinwray]

As we (from the FBCTF) project are getting some performance issue reports that seem to be related to HHVM, the inclusion of FBCTF as a target would be of much value.

Unfortunately, thus far through our own testing, we have been unable to reproduce the issues.