tls_read() and tls_write() may return TLS_WANT_POLLIN or TLS_WANT_POLLOUT
if data isn't ready to be read or written yet. We have to account for this
by converting it to EAGAIN, which is how a typical read() or write()
function should behave.
Also installed a SIGPIPE handler; we do not want to be terminated by
SIGPIPE, and it's safe to ignore this signal because it should be
handled thoroughly in the code.
This is useful for having a TLS and a non-TLS version port, like Synapse.
I verified that the multiple-servers does in fact work as intended,
although the TLS server part is broken; I must be doing something
incorrectly with LibreSSL in setting up the server.
This is the easiest and cleanest way to get logging into some of the
fundamental APIs, such as the database and TLS APIs. We don't want to
have to pass logging functions to those, but they can safely use the
global logging configuration.
