Remove the prev pointer from the filter chain. This removes

the complexity of trying to set the filter chain correctly, with the
side-effect of forcing us to walk the entire chain whenever we add
a filter.  Since the filter chains are small, the decrease in
complexity is worth it.
Reviewed by:	Allan Edwards


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93745 13f79535-47bb-0310-9956-ffa450edef68