Before this commit it was not clear that non-native SegWit outputs
(e.g. P2PKH or P2SH-P2WPKH) only work if the correct scriptSig is
provided.
This then also makes it more clear why P2SH-P2WPKH outputs are NOT
supported by the "simple" variant.
This commit adds a table that clarifies what script types are compatible
with what signing variant and also makes more clear what the exact
format for the signatures of the different variants are.
Both generating and verifying a proof allows for specifying a custom
generator point G. But that custom generator point was not passed into
the dleq_challenge function, resulting in the default (secp256k1)
generator point to be used. This lead to the test vectors being
incorrect.
Oli