Clean up blocking and non-blocking reads from buckets. The only bucket

that works correctly right now is sockets, but pipes are coming next.
This also makes the http_header_filter do AP_MODE_PEEK correctly.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86830 13f79535-47bb-0310-9956-ffa450edef68