Add standalone testbench for z80 core; run Patrik Rak tests on it

[lvd2]

Patrik Rak's tests (https://github.com/raxoft/z80test) are mainly targeted to the weird behaviour of F3/F5 flags during or after SCF/CCF commands. Here I've made a testbench to run them and collect logs.

These tests pass on real CMOS and NMOS Z80s, but not on this core, so it probably needs bugfixing.

More on SCF/CCF/F3/F5 could be found here: https://github.com/hoglet67/Z80Decoder/wiki/Undocumented-Flags#scfccf

A software library that is able to accurately emulate Z80 (all tests are passing) https://github.com/redcode/Z80

[ogamespec]

It's UB, unlikely to do nicely in a synthesised core