Use the recommended way to integrate Cython and NumPy

[fweimer-rh]

This follows the example code in https://cython.readthedocs.io/en/latest/src/tutorial/numpy.html#adding-types.

The previous version results in an int-conversion error with current compilers:

…-build/wrappers/python/freenect3.c:16598:3: error: returning ‘void *’ from a function with return type ‘int’ makes integer from pointer without a cast
16598 |   import_array();
      |   ^~~~~~~~~~~~

Related to:

• https://fedoraproject.org/wiki/Changes/PortingToModernC
• https://fedoraproject.org/wiki/Toolchain/PortingToModernC