Test TLS interoperability between LibreSSL and OpenSSL.

Implement simple SSL client and server in C.  Create four binaries
by linking them with LibreSSL or OpenSSL.  This way API compatibility
is tested.  Connect and accept with netcat to test protocol
compatibility with libtls.

Currently OpenSSL 1.0.2p from ports is used.  Plan is to move to
OpenSSL 1.1 and and test TLS 1.3.