Generating invalid signature

Generating invalid signature when passing identical arguments: 

```
 m  = Buffer.from("ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", "hex")
 d = Buffer.from("0000000000000000000000000000000000000000000000000000000000000001", "hex")
secp256k1.ecdsaSign(m,d) // bindings version
elliptical.ecdsaSign(m,d) // pure js version
```