Changes since the last release:
- fixed main screen memory contention alignment (#54).
- fixed debugger single-stepping just index prefixes (#53).
- fixed instruction trace showing double registers when only half changed.
- fixed step-out feature in debugger.
- fixed debugger benchmark mode still processing interrupts.
- fixed cancelled line interrupt end event showing in debugger.
- added 'tryvrr' option (default=true) to try Variable Refresh Rate video.
- added Ctrl modifier to run more instructions using the KP4/5/6.