A few instructions were missing flag setting entirely or were generating
wrong flags
- ROL, ROR, SHL, SHR, ASHR, SHLD, SHRD, CMPXCHG
This fixes those instructions and removes a few outdated comments
Specifically noticed when trying to run xcalc, it was using the flag
results from SHL for something and crashed without flag setting.
Unit tests for RFLAG setting instructions is still forthcoming