enhancements scope

Currently in Cython, one can do

#!python
f(1)

def f(x):
    print x

This doesn't work in Python. Also, if one does

#!python
def f(x):
    return x

f = math.sin
print f(10)

it doesn't do the same things as Python either.

We should probably at least simulate the correct behavior, without sacrificing the compile-time linking of module-level functions.

[:enhancements/scope/transformimpl: One approach to implementation]

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This doesn't work either:

#!python
class Bar(object):
    CONST = 25
    def foo(self, value=CONST):
        print value

This gives a compile-time error.