Merge r1529014 from trunk:

core: Add missing Reason-Phrase in HTTP response headers.
PR 54946.

Submitted by: rjung
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1530280 13f79535-47bb-0310-9956-ffa450edef68