Feature request: Expose hash128_x64

[felipeochoa]

Would be great to have this be callable from Python! Not super familiar with Cython, but if it were possible to convert a C array to a tuple, then I think it's just matter of creating a return variable uint32_t[4] out and sending that to python land.

[ofek]

@honnibal Hello! Any chance you could expose this variant soon?

[ofek]

or cc @ines 😄