I can't be the only person in need of this helper :) This should untangle

all of the complexities of building httpd against srclib/apr/ alone (along
with a seperate copy of srclib/expat/ owing to the removal of expat from
the apr tree).

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1129885 13f79535-47bb-0310-9956-ffa450edef68