Make httpd stricter with respect to TLS configuration - in particular, do

Make httpd stricter with respect to TLS configuration - in particular, do
not allow TLS and non-TLS to be configured on the same port, do not allow
TLS options to be specified without a TLS listener and ensure that the TLS
options are the same when a server is specified on the same address/port.
Currently, these configurations are permitted but do not work as intended.

Also factor out and reuse the server matching code, which was previously
duplicated.

ok reyk@