Update to PEP 227 (static scoping)

[Jeremy Hylton]

You're right that the PEP doesn't spend much time explaining the
motivation.  Just this paragraph in the introduction:

    The changed scoping rules address two problems -- the limited
    utility of lambda statements and the frequent confusion of new
    users familiar with other languages that support lexical scoping,
    e.g. the inability to define recursive functions except at the
    module level.

I'll expand this in the next draft.

Jeremy