Allow mod_ssl to send back an error message if an HTTP request is sent

Allow mod_ssl to send back an error message if an HTTP request is sent
over an HTTPS connection.  This also adds an ap_remove_input_filter
function, which should be used to remove the SSL input filter in this
case, as soon as this code is stressed a bit more.

For right now, we are sending the same message that we used to send in
mod_ssl for Apache 1.3.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk/modules/ssl@90724 13f79535-47bb-0310-9956-ffa450edef68