Fix tests cases.
Fix tests cases.

The way compact signatures are working was explain to me:

https://github.com/bitcoin/secp256k1/issues/45

apoelstra/rust-secp256k1,apoelstra/rust-secp256k1,arkpar/rust-secp256k1,arkpar/rust-secp256k1,arkpar/rust-secp256k1,apoelstra/rust-secp256k1,arkpar/rust-secp256k1,apoelstra/rust-secp256k1,arkpar/rust-secp256k1