Merge r1770951, r1774008, r1774068, r1774069 from trunk:

Allow for initual burst at full speed


Some "error" reporting if we overflow


rate limit notes


xhtml

Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1774071 13f79535-47bb-0310-9956-ffa450edef68