Looks to me like it was always defined,even if not given a value.
```
#if (defined(NPY_CPU_X86) || defined(NPY_CPU_AMD64))
#define NPY_CPU_HAVE_UNALIGNED_ACCESS
#else
#define NPY_CPU_HAVE_UNALIGNED_ACCESS 0
#endif
```
Header guards work that way. What am I missing?