RSS 1.0 miss some unique identifier

[casta]

According to the RSS 1.0 spec, RSS 1.0 feeds should use the "rdf:about" attribute of the to store the item identifier (see http://www.mnot.net/rss/tutorial/#RSS10).
A good feed example is http://kernel.org/kdist/rss.xml

When parsing this rss 1.0 feeds with simplepie, the Item->get_id() falls back to the link as ID, which is quite bad this it's not unique !
So here is a very small patch (on top of git master) that fixes this and try to use the rdf:about attribute in Item->get_id() before falling back to link. This fixes the feed handling :

diff --git a/SimplePie/Item.php b/SimplePie/Item.php
index 86e6ef4..35d6b6c 100644
--- a/SimplePie/Item.php
+++ b/SimplePie/Item.php
@@ -122,6 +122,10 @@ class SimplePie_Item
                        {
                                return $this->sanitize($return[0]['data'], SIMPLEPIE_CONSTRUCT_TEXT);
                        }
+                       elseif ($return = $this->data['attribs'][SIMPLEPIE_NAMESPACE_RDF]['about'])
+                       {
+                               return $this->sanitize($return, SIMPLEPIE_CONSTRUCT_TEXT);
+                       }
                        elseif (($return = $this->get_permalink()) !== null)
                        {
                                return $return;