Start keeping track of the amount of time taken to process a request again.

Results in the 'Req' field in mod_status no longer being bogus.

MFC: 149550
Reviewed by: jim, stas, geoff


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@151258 13f79535-47bb-0310-9956-ffa450edef68