Backport:

Further clarify the naming of the entity that originates the request by
calling that entity a useragent instead of a client.
Further clarify the naming of the entity that directly connects to us by
calling that entity a client instead of a peer.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1214022 13f79535-47bb-0310-9956-ffa450edef68