Implement PEP 3115 -- new metaclass syntax and semantics.

The compiler package hasn't been updated yet; test_compiler.py fails.
Otherwise all tests seem to be passing now.  There are no occurrences
of __metaclass__ left in the standard library.
Docs have not been updated.

Parser/Python.asdl

@@ -11,7 +11,12 @@ module Python version "$Revision$"
 
 	stmt = FunctionDef(identifier name, arguments args, 
                            stmt* body, expr* decorators, expr? returns)
-	      | ClassDef(identifier name, expr* bases, stmt* body)
+	      | ClassDef(identifier name, 
+			 expr* bases,
+			 keyword* keywords,
+			 expr? starargs,
+			 expr? kwargs,
+			 stmt* body)
 	      | Return(expr? value)
 
 	      | Delete(expr* targets)