Modify mod_include to send blocks of data no larger than 9k.

Without this, mod_include will wait until the whole file is parsed,
or the first tag is found to send any data to the client.
Submitted by:   Paul J. Reder <rederpj@raleigh.ibm.com>


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@88417 13f79535-47bb-0310-9956-ffa450edef68