Merge r1053523 from trunk:

PR50525: Header always ... doesn't really mean "always" in terms of what you 
can edit/merge/append/set since it only looks at r->err_headers_out and
the initial value may have lived in r->headers_out.





git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1053524 13f79535-47bb-0310-9956-ffa450edef68