Support update value for Solidity <0.5 #3
Description
Right now, for Solidity versions earlier than 0.5, we skip variable update hooks completely. The reason is that pre-0.5 Solidity does not support abi.encode.
However, since keccak256 exists pre-0.5, we should be able to support primitive types and simple dynamic types. That would allow partial support for update hooks in legacy contracts.