Description:
------------
the php function unlink can't handle posix acls. The function is_writeable **can** handle posix acls. See #34957


my acl on file 'foo':
----------------------
# file: foo
# owner: jonas.genannt
# group: users
user::rw-
group::r-x                      #effective:r--
group:www-data:rw-
mask::rw-
other::---

The php script runs as user www-data and group www-data. 

The function unlink fails on posix acls but is_writeable seems to be handling posix acls.



Reproduce code:
---------------
<?php
if (is_writeable('foo')) {
        echo "fooo is Writeable<br/>";
        if (unlink('foo')) {
                echo "Removed!";
        }
        else {
                echo "NOT REMOVED!<br/>";
        }
}
?>

Expected result:
----------------
fooo is Writeable
Removed

Actual result:
--------------
fooo is Writeable
Warning: unlink(foo) [function.unlink]: Permission denied in test.php on line 4
NOT REMOVED!