Add noexcept to _utils C-equiv functions

The functions in `_utils` are effectively straight C functions. In
Cython 0.x, these would have been treated as `noexcept` by default.
However in Cython 3.x all functions are treated as potentially raising
exceptions (including these). While that is a sensible default in
general, these functions still won't raise exceptions. So tidy things up
by adding `noexcept` to turn off the additional Cython checks emitted in
and around them.

Author: jakirkham

docs/release.rst

@@ -11,6 +11,12 @@ Release notes
 Unreleased
 ----------
 
+Fix
+~~~
+
+* Add `noexcept` to `_utils` C-equiv functions
+  By :user:`John Kirkham <jakirkham>`, :issue:`641`.
+
 
 .. _release_0.14.0:
 

numcodecs/_utils.pxd

@@ -8,14 +8,14 @@
 from libc.stdint cimport uint8_t, uint32_t
 
 
-cdef inline void store_le32(uint8_t c[4], uint32_t i) nogil:
+cdef inline void store_le32(uint8_t c[4], uint32_t i) nogil noexcept:
     c[0] = i & 0xFF
     c[1] = (i >> 8) & 0xFF
     c[2] = (i >> 16) & 0xFF
     c[3] = (i >> 24) & 0xFF
 
 
-cdef inline uint32_t load_le32(const uint8_t c[4]) nogil:
+cdef inline uint32_t load_le32(const uint8_t c[4]) nogil noexcept:
     return (
         c[0] |
         (c[1] << 8) |