Add note about supported filesystems.

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@166726 c90b9560-bf6c-de11-be94-00142212c4b1

reference/xattr/reference.xml

@@ -1,5 +1,5 @@
 <?xml version='1.0' encoding='iso-8859-1'?>
-<!-- $Revision: 1.1 $ -->
+<!-- $Revision: 1.2 $ -->
 <!-- Generated by xml_proto.php v2.0. Found in /scripts directory of phpdoc. -->
  <reference id="ref.xattr">
   <title>xattr Functions</title>
@@ -19,6 +19,11 @@
      To use xattr, you will need libattr installed, available
      on the Linux XFS homepage <ulink url="&url.xattr;">&url.xattr;</ulink>.
     </para>
+    <para>
+     Note that these functions work only on filesystems that support extended 
+     attributes (on Linux 2.6: ext2, ext3, reiserfs, jfs and xfs) and have them 
+     enabled at mount time. Ask your system administrator if in doubts.
+    </para>
    </section>
 
    &reference.xattr.configure;