Problems in derivation with testnet

[elbelga]

Hi, I believe that there is a problem in derivation and some time doesn't work well. I made some tests with testnet and validate results with https://iancoleman.io/bip39/ and it doesn't match.

I found that in the file internal.m (line 130) you save new private key like this

        result = [NSMutableData dataWithLength:numBytes];
        BN_bn2bin(privateKey, result.mutableBytes);

and I believe that you need to save new private key like this

        result = [NSMutableData dataWithLength:32];
        BN_bn2bin(privateKey, &result.mutableBytes[32-numBytes]);

Regards