[ENH] MsecClockValueOptimization-nk ( [sm][et] small, straightforward, recommend approval )

[cdshaffer at acm.org]

Ned just manually "inlined" a primitive callout.  Seems safe enough.  I
wouldn't really expect the performance impact of this improvement to be
very easily measured with existing benchmarks but I would feel remiss if
I didn't at least run them.  Using the Benchmarks package on SqueakMap:
Slopstone and Smopstone showed no real improvement, I couldn't get the
MacroBenchmarks to run in 5816 and don't have time to sort it out now. 
Recommend approval.