Backport:

mod_log_config: Add the R option to log the handler used within the
request.
Submitted by: Christian Folini <christian.folini netnea com>
+1: minfrin, jim, rpluem


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@917009 13f79535-47bb-0310-9956-ffa450edef68