Function lpn::lf1::fwht

pub fn fwht(data: &mut [i64], bits: u32)

Fast Walsh Hamadard Transform

Adapted from Bogos, Tramer, Vaudenay, who used http://www.musicdsp.org/showone.php?id=18

Data: data to transform the transform over (whoooah) bits: log2(size), the length of the data