Merge r1481302, r1481397 from trunk:

mod_proxy: Reject invalid values for Max-Forwards.


Adjust format string

type was changed by r1481302

Submitted by: minfrin, sf
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1485673 13f79535-47bb-0310-9956-ffa450edef68