wyhash.h: use uint32_t instead of unsigned
wyhash.h: use uint32_t instead of unsigned

On some platforms usigned may be larger than 32 bits and on non-POSIX
platforms unsigned may even be _smaller_ than 32 bits, yet 32 bits are
required here. To ensure this holds, use uint32_t from stdint.h.

wangyi-fudan/wyhash,wangyi-fudan/wyhash