Remove misleading comment about type-class unification.

Doc/lib/libstdtypes.tex

 \section{Built-in Types \label{types}}
 
 The following sections describe the standard types that are built into
-the interpreter.  Historically, Python's built-in types have differed
-from user-defined types because it was not possible to use the built-in
-types as the basis for object-oriented inheritance. With the 2.2
-release this situation has started to change, although the intended
-unification of user-defined and built-in types is as yet far from
-complete.
+the interpreter.
+\note{Historically (until release 2.2), Python's built-in types have
+differed from user-defined types because it was not possible to use
+the built-in types as the basis for object-oriented inheritance.
+This limitation does not exist any longer.}
 
 The principal built-in types are numerics, sequences, mappings, files
 classes, instances and exceptions.