Document the special APACI behavior for installation paths where

``/apache'' is appended to paths under some (well defined, of course)
situations to prevent pollution of system locations with Apache files.

PR: 2660


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@81802 13f79535-47bb-0310-9956-ffa450edef68