SF patch 672098: Three __contains__ implementations

Contributed by Jp Calderone.
diff --git a/Lib/xml/sax/xmlreader.py b/Lib/xml/sax/xmlreader.py
index f1c9d9d..9a2361e 100644
--- a/Lib/xml/sax/xmlreader.py
+++ b/Lib/xml/sax/xmlreader.py
@@ -321,6 +321,9 @@
     def has_key(self, name):
         return self._attrs.has_key(name)
 
+    def __contains__(self, name):
+        return self._attrs.has_key(name)
+
     def get(self, name, alternative=None):
         return self._attrs.get(name, alternative)