core: set ap_request_core_filter() last.

Since it may retain data and should run after other "request" filters, use
the last possible position for a "request" filter: AP_FTYPE_CONNECTION - 1.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1837131 13f79535-47bb-0310-9956-ffa450edef68