Make sure the "includedir" gets PREFIX/include/apache if PREFIX not already

contains the words "apache" to make sure Apache headers do not bristle a
standard include directory. Just the same behaviour as already for
"sysconfdir", "datadir" and "localstatedir". Thanks to Marc for discovering
this bug.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80910 13f79535-47bb-0310-9956-ffa450edef68