sync with trunk to silent compiler warnings.

Backport of r1481677, r1494317, r1488496.
Reviewed by: fuankg, gsmith, minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1494568 13f79535-47bb-0310-9956-ffa450edef68