A brand new implementation of Profile.calibrate(). This measures an

actual run of the profiler, instead of timing a simplified simulation of
part of what the profiler does.  It computes a constant about 60% higher
on my Win98SE box than the old method, and the new constant appears much
more realistic.  Deleted the undocumented simple(), instrumented(), and
profiler_simulation() methods (which existed only to support the previous
calibration method).