libevent2 can still somehowe call client_read even in code paths
that never enable reading from the evbuffer. Can't reproduce on
the libevent in base on OpenBSD. It's a bit ugly, but it's a small
workaround for something that otherwise *always* make gmid crash
when linked against libevent2. (client_read works under the
assumption that c->host != NULL, matched_proxy crashes otherwise.)
The tests are still there, the suite is equivalent to the old one, but
this one is better structured.
The biggest annoyance I had with the old one was that it wasn't
straightforward to test only a specific set of tests. It's still
impossible, but it's way easier to do it now.
This extract all the tests to their own functions. It's overall
better in all possible regards.