Merge r1826686 from trunk:

Instrument 'md_log_perror' and fix corresponding errors reported by gcc.


Submitted by: jailletc36
Reviewed by: jailletc36, ylavic, covener


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1827108 13f79535-47bb-0310-9956-ffa450edef68