Bump to signature 3

[baloo]

alternative to #505

[tarcieri]

Is this really still needed?

[baloo]

error[E0282]: type annotations needed
   --> src/pkcs1v15.rs:461:35
    |
461 |             let out = signing_key.sign(text.as_bytes()).to_bytes();
    |                                   ^^^^
    |
help: try using a fully qualified path to specify the expected types
    |
461 -             let out = signing_key.sign(text.as_bytes()).to_bytes();
461 +             let out = <pkcs1v15::signing_key::SigningKey<CoreWrapper<Sha1Core>> as Signer<S>>::sign(&signing_key, text.as_bytes()).to_bytes();
    |

For more information about this error, try `rustc --explain E0282`.

Without it.

In the end I think #505 creates less changes to the downstream consumer.

[tarcieri]

I think the blanket impl is legitimately breaking inference for the case there's an explicit Signer impl instead of using the blanket one, which would be a case of RustCrypto/traits#1831

[baloo]

agreed

[baloo]

Closed in favor of #513