Create a library out of example_host

[axic]

The example_host already implements a lot of what a minimal client for testing needs.

It may make sense creating a library out of it, so that it could be shared with Solidity. This library could be provide a C++ interface wrapping everything needed for testing (aka a memory-only single node client).

@chfast @chriseth what do you think?

[chfast]

Not bad idea, I already use it for EVMC testing.

[axic]

To bad idea, I already use it for EVMC testing.

Too bad?

[chfast]

To bad idea, I already use it for EVMC testing.

Too bad?

ToNot. I should not work at nights.

[chfast]

Here is more functional one: https://github.com/ethereum/evmone/blob/master/test/utils/host_mock.hpp
Used for evmone unit testing and EVM fuzzing.

[axic]

The Solidity version of this is here:

• https://github.com/ethereum/solidity/blob/develop/test/EVMHost.cpp
• https://github.com/ethereum/solidity/blob/develop/test/EVMHost.h