Check hostname of proxy back end server against certificate
Check hostname of proxy back end server against certificate

Previously, the server certificate was only checked for validity. With
this commit, mod_gnutls gets the expected hostname from the note
"proxy-request-hostname" which should have been set by mod_proxy and
matches it against the server certificate.

airtower-luna/mod_gnutls,airtower-luna/mod_gnutls,airtower-luna/mod_gnutls