Merge r1463056 from trunk:

Use %pm available since apr 1.3 instead of an extra call to apr_strerror

Submitted by: sf
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1470526 13f79535-47bb-0310-9956-ffa450edef68