Merge r1700851 from trunk:

mod_negotiation: simplify type-map body tag lookup, and be safe
should it contain a NUL byte.

Submitted by: ylavic
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1703406 13f79535-47bb-0310-9956-ffa450edef68