Ethereum Foundation

### What is wrong?

A number of functions defined in [std::evm](https://github.com/ethereum/fe/blob/master/crates/library/std/src/evm.fe) take offsets and lengths for regions of memory and calldata. These should take [buffer](https://github.com/ethereum/fe/blob/master/crates/library/std/src/buf.fe) types instead.

### How can it be fixed

- implement `CalldataBuffer`, `CalldataBufferReader`
- update `revert_mem`, `return_mem`, `call_data_copy`, `code_copy`, `ext_code_copy`, `keccak256_mem`, `create`, `create2`, `call`, and `log` 

run `$ cargo test std_lib` to check changes made to `crates/library`

`std::evm` functions should take buffer types

INSTRUCTIONS

What is wrong?

How can it be fixed