Large integer literals/constants can generate invalid C code

[scoder]

The perfectly valid Python code

def test():
    return 1L << 200

generates either

PyInt_FromLong(1L << 200)

without constant folding, or

PyInt_FromLong(1606938044258990275541962092341162602522202993782792835301376)

with constant folding enabled. Both do not work in C.

[scoder]

The new behaviour is that Cython will convert integer literals that do not fit into signed 32bits into Python objects, unless explicitly coerced into a C integer, e.g. in typed assignments. This assures that literals do not unexpectedly loose bit precision.