Allow mod_autoindex to serve symlinks if permitted and optimize our stats

Allow mod_autoindex to serve symlinks if permitted and optimize our stats
so that only one stat() is needed.

If we get APR_FINFO_MIN bits, lookup_dirent won't do a repeated stat()
call.  So, let's do it here.  Also, if we see a symlink, expand it.
(Technically, we don't *have* to expand the symlinks - the resolve_symlink
fix handles that, but we can't really assume that.)  Since we know that
dirent will be rr->finfo anyway, go back to relying on dirent only for
APR_DIR checks.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93329 13f79535-47bb-0310-9956-ffa450edef68