StringData uses murmurhash for it's hashing function. On 32 bit systems it returns a little endian decoded uint32_t of the 32 bit hash output. On 64 bit systems it returns a little endian decoded uint64_t of the 128 bit hash output.

We should pick something better than murmur, cityhash perhaps (then we could pick something better and stop generating 128 bits of hash only to throw half of it away)