Fix byte range content length calculations, which should fix the reported

problems with byteserved PDFs. I've had a couple of reports that things
work OK with this patch but more testing would be good.
PR: 6711


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@86847 13f79535-47bb-0310-9956-ffa450edef68