The ap_add_input_filter/ap_add_output_filter functions do an O(n) scan

through the list of registered filters.  This patch replaces the linear
list with a hash table for better performance.
Submitted by:	Brian Pane <bpane@pacbell.net>
Reviewed by:	Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@90888 13f79535-47bb-0310-9956-ffa450edef68