Merge r1745034 from trunk:

PR59612: Print the ap_expr() error message when an expression cannot
be evaluated in forward-dns provider.

Submitted By: Tianyin Xu <tixu cs.ucsd.edu>
Committed By: covener


Submitted by: covener
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1747717 13f79535-47bb-0310-9956-ffa450edef68