review/test/vote on the apxs fixes

some day when I'm bored I may teach it to avoid duplicating the same -I
directory multiple times (when at least 2 of httpd, apr, apr-util are
installed in the same location), but that is relatively unimportant


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@99985 13f79535-47bb-0310-9956-ffa450edef68