Short-circuit leading zeros on power.
Seven bytes instruction; big save on small exponents.
Make 64 bit clean; costs 3 bytes.
Merge branch 'master' into power_short_circuit
Cost down to 5 (232).

Conflicts:
	rmsim.cc
Merge branch 'master' into clean64
Cost is still 3 bytes; 230.
Merge branch 'master' into power_short_circuit
Cost still 5 (216).
Conflicts:
	rmsim.cc
Simplify; no change.
Merge branch 'master' into power_short_circuit
Cose still 5 (216).
Conflicts:
	rmsim.cc
Take loads outside of loop; no change.
Trivial fixes.
Rename file
Merge branch 'master' into power_short_circuit
Merge branch 'master' into clean64
And obvious bug fix.

Conflicts:
	rmsim.cc
Backlog
Merge branches 'clean64' and 'power_short_circuit'