Add bindings to SSL_bytes_to_cipher_list

[RoastVeg]

I have a use case where I need to change the SSL context on the server side based on the supported cipher suite provided in the client hello callback. Without SSL_bytes_to_cipher_list support in rust-openssl, there really isn't a convenient way to handle the output from client_hello_ciphers, as the format is a real mess.

[sfackler]

I generally prefer to bind to each OpenSSL API as directly as possible, so I think we'd want separate methods for SSL_client_hello_get0_ciphers, SSL_bytes_to_cipher list, and SSL_client_hello_isv2 (though really the answer to that is just false as this point!).

[RoastVeg]

In that case as SSL_client_hello_get0_ciphers and SSL_client_hello_isv2 both already have bindings, would you accept a new method like the following?

// struct Ssl
#[corresponds(SSL_bytes_to_cipher_list)]
pub fn bytes_to_ciphers_stack(&self, bytes: &[u8], isv2format: bool) -> Option<(Stack<SslCipher>, Stack<SslCipher>)> { // ... }

Although I don't know where else this method is useful, it would have the added benefit of being usable outside of the client hello callback.

[sfackler]

Can we have this return a struct CipherLists { pub suites: Stack<SslCipher>, pub signaling_suites: Stack<SslCipher> } so it's a bit more descriptive?

[sfackler]

Does the function not push errors onto the stack on failure, or should this return a Result<CipherLists, ErrorStack> instead?