Optionally allow non-SSL connections on same port as SSL

If enabled one listening socket will accept both SSL and plain HTTP connections.

Do not enable if you regard SSL handshake as some kind of security, eg, use
client-side certs to restrict access.

AG: changed flag names, added extra comments, changelog, add -a in test server

Signed-off-by: James Devine <fxmulder@gmail.com>
Signed-off-by: Andy Green <andy@warmcat.com>