Request: Easy 'rewind time' option while debugging.

[VectorEyes]

When debugging issues such as spurious NMIs, it would be really helpful to be able to say 'rewind 2000 cycles' so you could then start tracing. A big button saying 'rewind by 10/20/50/100 etc. cycles' would speed up debugging in scenarios where it takes you ages to debug to the point where an anomalous event occurs.