BytesLib.sol
All functions in BytesLib have some require check for overflow. However, these checks will only work with Solidity version < 0.8 because Solidity 0.8 already has some overflow check. 
For example, in the function slice(), in the case overflow actually happens in the first check, the calculation _length + 31 is already revert by solidity 0.8 before checking the condition in the require.
