Implement a test framework

Implement a test framework running a set of test suites for functionality, regression, resource utilisation, and fuzzing.

Here's an incomplete list of tests that should be supported.

Functional
- TCP session setup, client and server side
- TLS session setup, client and server side, negotiating
  - TLS1.0
  - TLS1.1
  - TLS1.2
- DTLS session setup, client and server side, negotiating
  - DTLS1.0
  - DTLS1.2
- Various versions of OpenSSL
  - FIXME
- Cert validation
  - CA handling
  - TODO
- Attribute rewrite
  - TODO
- CRL handling
- F-Ticks generation
- Message forwarding, for all four transports
  - AUTH req => successful response
  - AUTH req => time out
  - AUTH req => "bad encryption"
  - TODO

Memory leaks (using valgrind?)
- TODO

Fuzzing (incl. ASAN?)
- TODO