* generalize from error buckets to metadata buckets

* also applicable to the deflate input filter
* pass along metadata buckets rather than giving up mid-stream

vastly improved by: Rüdiger Plüm


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@556028 13f79535-47bb-0310-9956-ffa450edef68