Add ReceiveBufferSize directive to control the TCP receive buffer.

Submitted by: Eric Covener <covener gmail.com>
Reviewed by:  Justin Erenkrantz (with minor formatting tweaks)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@157583 13f79535-47bb-0310-9956-ffa450edef68