Bug in InStream.readinto()

[samuelgarcia]

Ensure number_of_samples_per_channel is int (and not numpy.int)
Otherwise ctype is buggy in _read_raw.

[campagnola]

Here's an exception I encountered that would be fixed by this PR:

Traceback (most recent call last):
  File "our_code\ni_daqmx.py", line 232, in run
    nb_sample = aitask.in_stream.readinto(raw_data_flat)
  File "C:\Anaconda3\lib\site-packages\nidaqmx\_task_modules\in_stream.py", line 1992, in readinto
    self.timeout)
  File "C:\Anaconda3\lib\site-packages\nidaqmx\_task_modules\read_functions.py", line 583, in _read_raw
    ctypes.byref(number_of_bytes_per_sample), None)
ctypes.ArgumentError: argument 2: <class 'TypeError'>: wrong type

[rares-pop]

Thank you for the contribution!

[samuelgarcia]

cool!!