Poseidon hash has changed

[nanaknihal]

Similar to issue #13
Old and new versions of circomlibjs give different Poseidon functions with different outputs for the same inputs. Perhaps this is intentional, as I see it passes test/poseidon.js. However, the old version seems to be more compatible with other Poseidon implementations, whereas the new version does not pass tests when comparing to other Poseidon implementations.

To reproduce:

npm i circomlibjs-old@npm:[email protected]
npm i circomlibjs-new@npm:[email protected]

const { buildPoseidon } = require("circomlibjs-new");
const { poseidon } = require("circomlibjs-old");
const { ethers } = require("ethers");
const oldIsNew = async () => {
    const oldPoseidon = await buildPoseidon();
    const newPoseidon = poseidon;
    console.log(
        ethers.BigNumber.from(oldPoseidon([1,2,3,4,5])),
        "is",
        ethers.BigNumber.from(newPoseidon([1,2,3,4,5])) 
    )
}

oldIsNew()

Output:

> BigNumber {
  _hex: '0x6e2f2d34107fa746e4ac7bfdf5cceafa076c606db07e7391806811e85434bb01',
  _isBigNumber: true
} is BigNumber {
  _hex: '0x0dab9449e4a1398a15224c0b15a49d598b2174d305a316c918125f8feeb123c0',
  _isBigNumber: true
}

As you can see, it gives a different value for poseidon([1,2,3,4,5])