generator expressions do not work in closures

[scoder]

# cython: language_level=3

def list_comp_in_closure():
    """
    >>> list_comp_in_closure()
    [0, 4, 8]
    """
    x = 'abc'
    def f():
        return x
    result = [x*2 for x in range(5) if x % 2 == 0]
    assert x == 'abc' # don't leak in Py3 code
    assert f() == 'abc' # don't leak in Py3 code
    return result

generates invalid C code: the loop variable is defined in the closure struct but has a different name inside of the function code.

[scoder]

Test case added in

 http://hg.cython.org/cython-devel/rev/b1f04712264b

[scoder]

Fix is here:

 http://hg.cython.org/cython-devel/rev/31aa1c2064ae