xxhash.go
func NewS64(seed uint64) (xx *XXHash64) {
	xx = &XXHash64{
		seed: seed,
	}
	xx.Reset()
	return
}
func NewS64(seed uint64) (xx *XXHash64) {
	xx = &XXHash64{
		seed: seed,
	}
	xx.Reset()
	return
}
// NewS64 creates a new hash.Hash64 computing the 64bit xxHash checksum starting with the specific seed.