[Feature request] Prefix on the salt

[ethermachine]

Metamorphic is a popular complementary tool, with factories for multiple contracts deployed on mainnet.

To avoid front-running / stealing of selfdestructed addresses (because the functions on the deployed factories are public), they enforce that the first 20bytes of the salt must match the msg.sender.

This is a request to include another input flag, that when non-empty, would be the prefix of the calculated salts.

[acegilz]

To avoid front-running / stealing of selfdestructed addresses (because the functions on the deployed factories are public), they enforce that the first 20bytes of the salt must match the msg.sender.

This is achievable with https://github.com/0age/create2crunch