Fixed out-of-bounds when generating random on Windows

[Skielex]

The function

@datagen("i64")
def uniform():
    return np.random.randint(-(2**63), 2**63, size=max_n)[:n]

raises an error on Windows due to using i32 type.

Traceback (most recent call last):
  File "...\generate_randoms.py", line 352, in <module>
    data = f()
  File "...\generate_randoms.py", line 129, in uniform
    return np.random.randint(-(2**63), 2**63, size=max_n)[:n]
  File "numpy\\random\\mtrand.pyx", line 780, in numpy.random.mtrand.RandomState.randint
  File "numpy\\random\\_bounded_integers.pyx", line 2877, in numpy.random._bounded_integers._rand_int32
ValueError: low is out of bounds for int32

Specifying dtype=np.int64 fixes this.