np.long breaks choice(p=...) and permutation(int) on NumPy 1.26 #194

mkl_random/mklrand.pyx uses np.long at lines 2829, 2844 and 7100, but np.long does not exist in NumPy 1.24-1.26; it was only reintroduced in NumPy 2.0. The runtime floor in pyproject.toml is numpy >=1.26.4, so an installation satisfying our own requirements fails:

choice(5, 3, p=[0.2] * 5)   -> AttributeError: module 'numpy' has no attribute 'long'
permutation(5)              -> AttributeError: module 'numpy' has no attribute 'long'

CI does not catch this because its matrix starts at NumPy 2.2. Fix by replacing np.long with an explicit C-long dtype, or by raising the NumPy floor to 2.0.

Found during review of gh-192.