remove call to ConfigHandler::replacePath() when resolving autoload.ini entries.
replace is_readable() call with a silenced fopen(), which will check our include path for the file specified.

*BREAKAGE WARNING*
this means is that you must have a full path specified in autoload.ini.  "lib/blah.class.php" (to reference "/path/to/mywebapp/lib/blah.class.php") would no longer work - unless /path/to/mywebapp is in your include_path of course :)  This should only be a problem for user-provided autoload.ini entries, as the "stock" ones all reference the %AG_APP_DIR% constant to provide a full path.