Fixed issue #48

[oleksandr-pavlyk]

Closes #48

(bld_npy_120) [10:26:23 vmlin03 mkl_fft]$ python issue48.py
fftn on full array: 680 ms
loop of fftn on subarray: 630 ms
True
(bld_npy_120) [10:26:32 vmlin03 mkl_fft]$ python issue48.py
fftn on full array: 656 ms
loop of fftn on subarray: 677 ms
True

Also fixes typo in _numpy_fft.py introduced in the previous commit.

@AndresGuzman-Ballen @mvandeput

[AndresGuzman-Ballen]

👍