sslh: update to 1.20.

v1.20: 20NOV2018
Added support for socks5 protocol (Eugene Protozanov)

New probing method:
Before, probes were tried in order, repeating on the
same probe as long it returned PROBE_AGAIN before
moving to the next one. This means a probe which
requires a lot of data (i.e. returne PROBE_AGAIN for
a long time) could prevent sucessful matches from
subsequent probes. The configuration file needed to
take that into account.

Now, all probes are tried each time new data is
found. If any probe matches, use it. If at least one
probe requires more data, wait for more. If all
probes failed, connect to the last one. So the only
thing to know when writing the configuration file is
that 'anyprot' needs to be last.

Test suite heavily refactored; `t` uses `test.cfg`
to decide which probes to test and all setup is
automatic; probes get tested with 'fast' (entire
first message in one packet) and 'slow' (one byte at
a time); when SNI/ALPN are defined, all combinations
are tested.

Old 'tls' probe removed, 'sni_alpn' probe renamed as 'tls'.
You'll need to change 'sni_alpn' to 'tls' in
your configuration file, if ever you used it.

(wiz)