Any failure in apr_stat on a symlink currently gives

Any failure in apr_stat on a symlink currently gives
"Symbolic link not allowed", which results in much head-scratching
if the actual problem is a broken link of some sort.  The real
fix would be to propogate the correct apr_stat error into the
error log, but that would require more refactoring than I'm
prepared to do.  This change simply expands the error message
to include both possibilities.  It improves the situation for
PR28515 but does not solve it.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@280018 13f79535-47bb-0310-9956-ffa450edef68