Need to check minsret for all tests that have deterministic# of instructioni

[allenjbaum]

There are cases specifically involving traps and interrupts which may or may not increment the minstret CSR.
To test for this, the trap handler, at the end installation, should save the value of minstret in the signature area (or elsewhere ini memory, and should read it again just before halting, subtract it from the first reading, and save the delta in the signature.
If possible, there should also be a debug mode that recalculates the delta and saves it at the end of each test, enabled by a command line switch. Taht may if there is a mismatch it will be far easier to see where that happened.