HTTP proxy ProxyErrorOverride: Leave 1xx and 3xx responses alone. Only

processing of error responses (4xx, 5xx) will be altered.

PR: 39245

This is based on a patch submitted by Bart van der Schans <schans hippo.nl>
and tweaked slightly by me based on discussions on dev@ since April 2006.
I think rpleum was the first to mention the 1xx issue.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@527969 13f79535-47bb-0310-9956-ffa450edef68