Description:
------------
The FileSystemIterator defines a few constants to mask its flags: CURRENT_MODE_MASK and KEY_MODE_MASK. However, there are other flags (SKIP_DOTS and UNIX_PATHS) which cannot be masked of by a constant. 

However, internally, there is a mask constant defined (SPL_FILE_DIR_OTHERS_MASK). It makes sense that this value is also known in PHP userland by the OTHER_MODE_MASK constant.

The attached patch adds this constant and is compatible with trunk, php_5_4 and php_5_3 branches.

Test script:
---------------
<?php
$it = new fileSystemIterator(".", FileSystemIterator::SKIP_DOTS | FileSystemIterator::CURRENT_AS_SELF);
$masked_flags = ($it->getFlags() & FileSystemIterator::OTHER_MODE_MASK);
print $masked_flags;

Expected result:
----------------
4096

Actual result:
--------------
PHP Notice:  Use of undefined constant OTHER_MODE_MASK - assumed 'OTHER_MODE_MASK'