Incorrect implementation of EIP 86

[nhynes]

The specification of EIP 86 suggests that new contracts be created using the semantics of the CREATE2(value, salt, mem_start, mem_size) opcode. Primarily, this requires new contract addresses be created from hash(sender + salt + code_hash).

Currently it seems that Parity does not match the spec since:

• FromSenderAndCodeHash does not include a salt, which prevents a contract from calling CREATE2 multiple times
• create_address_scheme uses FromCodeHash as its post-eip86 default
• the implementation of CREATE2 is not only unsalted but also fails to pop all four arguments off the stack

Hopefully I'm not missing something very basic here.

[Tbaut]

@sorpaas can you help?

[sorpaas]

salt is added after EIP-86 is implemented in Parity. That's why we didn't have it. I'll fix this.

One thing we need to take note is that this would break backward compatibility -- for current chain specs with eip86Transition implemented, it will no longer work. One way to fix this is to introduce a new flag (i.e. to support two different versions of EIP-86). I think that maintenance cost is high and I'm not sure whether there are actually chains using this feature right now. So I think I'm going to create the PR using the breaking backward compatibility route.