update a test compile to find apr.h when apr isn't in srclib

(the only one of several such places in Apache which
didn't get fixed to work with separate APR...  no fun
when v4 sockets won't talk to Apache anymore)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@98595 13f79535-47bb-0310-9956-ffa450edef68