EVM JIT connector

EVN JIT connector for C++ client. The JIT itself is a separated repo [ethereum/evmjit](https://github.com/ethereum/evmjit) linked to cpp-ethereum as a git submodule.

https://github.com/imapp-pl/ethereum/wiki/EVMJIT

It currently is integrated with TestEthereum and can be enabled with `--jit` command line option.

It's time to start asking questions...