Report OpenSSL errors on the server side verbosely

When SSL_accept() failed, we really need to look at the complete
error queue to be able to figure out what is happening.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Do not try to verify non-existing keys

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Extend LibVNCServer's GNUTLS code to allow anonymous TLS

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Initial, rudimentary server-side support for VeNCrypt

So far, we only support TLSNone, and only when linking to GNUTLS.

It's a start.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Support anonymous TLS on the server side even with OpenSSL

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>