Optimizations and one intentional loophole by Jim Fulton.

Optimizations and one intentional loophole by Jim Fulton.

The optimizations consist mostly of using local variables to cache
methods or instance variables used a lot (e.g. "self.write").

The loopholes allows marshalling extension types as long as they have
a __class__ attribute (in which case they may support the rest of the
class piclking protocol as well).  This allows pickling MESS extension
types.