Add tests and fix some small bugs they uncovered

Added a simple C server that basically mimics the "legacy" target applications, and a bash script to run it with various tlsinterposer options and verify the behavior.  The OpenSSL s_client utility is used as the client to connect to the test server.

Most of the options are tested.  I didn't do `-comp` and `+sslv2`, because it seems like compression and SSLv2 are disabled on the OpenSSL build I'm using from Ubuntu.  `-comp` might be more worthwhile to test eventually though, since compression can open attack vectors (like BEAST, CRIME).