Honor ssl-bump option for https_port.

Honor ssl-bump option for https_port.

Initial ssl-bump handling logic mimics that of http_port: If the option is
set, check the slow ssl_bump ACL, and if there is a match, plug into
switchToHttps() code path, generating a dynamic certificate and establishing a
secure connection with the client. If there is no match, Squid becomes a TCP
tunnel for the intercepted connection.

For now, we use the destination IP address of the intercepted connection as
the host name for the certificate (which will trigger browser warnings, of
course).