As long as there is no mature test suite for the library, only a test
in production could show failures. Tests must contain a huge workload
of active connections and various, unusual protocols.
No commit before test suite is complete.
```
$ make test
1_instance:1_singleinit -> passed [0.004s]
1_instance:2_destroynull -> expected_failure: Code expects valid pointer. [0.014s]
1_instance:3_multiinit -> passed [0.004s]
1_instance:4_multiinstance -> passed [0.036s]
2_natout:1_simplemasq -> passed [0.003s]
2_natout:2_unregistered -> passed [0.003s]
2_natout:3_cgn -> passed [0.003s]
2_natout:4_udp -> passed [0.003s]
2_natout:5_sameport -> passed [0.003s]
2_natout:6_cleartable -> passed [0.003s]
2_natout:7_stress -> passed [8.880s]
```