Added a 'sync' method to shelve.  If the underlying database does not have a sync
attribute, this method silently ignores this fact.  The default (bsddb's dbhash) does.
diff --git a/Lib/shelve.py b/Lib/shelve.py
index b05c627..8f709a2 100644
--- a/Lib/shelve.py
+++ b/Lib/shelve.py
@@ -72,6 +72,10 @@
 	def __del__(self):
 		self.close()
 
+	def sync(self):
+		if hasattr(self.dict, 'sync'):
+			self.dict.sync()
+	    
 
 class BsdDbShelf(Shelf):
 	"""Shelf implementation using the "BSD" db interface.