Backport from 2.1:

core_output_filter: don't split the brigade after a FLUSH bucket if
it's the last bucket.  This prevents creating unneccessary empty
brigades which may not be destroyed until the end of a keepalive
connection.

Submitted by: Juan Rivera <Juan.Rivera@citrix.com>
Reviewed by: Brian Pane, Jeff Trawick, Justin Erenkrantz, Sander Striker


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@100424 13f79535-47bb-0310-9956-ffa450edef68