mod_filter: Allow mod_filter to undo equiv of change=yes that was

baked into a filter provider.

trunk patch: http://svn.apache.org/r1519475

Submitted by: covener
Reviewed by: jim, minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1523242 13f79535-47bb-0310-9956-ffa450edef68