Move where the CORE_IN filter is added to the server. We used to do this

Move where the CORE_IN filter is added to the server.  We used to do this
in ap_new_connection, but that is bogus, because then other modules can't
put their own filter in.  Now, we do this in a new pre-connection hook
function.  Later, we will want to add some checking to make sure that this
is really an HTTP request that we are adding the filter for.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86364 13f79535-47bb-0310-9956-ffa450edef68