Perform run-time query in apxs for apr and apr-util's includes.

This is required when they are in disjoint directories from httpd.  Otherwise,
apxs won't pass their include information into the compiler and the
compilation will fail.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@99981 13f79535-47bb-0310-9956-ffa450edef68