Backport r1091330:

Allow apr and apr-util to be in 2 different location.
Otherwise: apr_version.h is not found when apr-util is tested.

Submitted by: jfclere
Reviewed by: rjung, rpluem, jorton


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1343914 13f79535-47bb-0310-9956-ffa450edef68