Add NumPy declarations for Cython 3.0 and later
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The pxd declarations for Cython 3.0 were improved to avoid using deprecated
NumPy C-API features.  Extension modules built with Cython 3.0+ that use NumPy
can now set the C macro ``NPY_NO_DEPRECATED_API=NPY_1_7_API_VERSION`` to avoid
C compiler warnings about deprecated API usage.