Enable this in CS for PowerPC; disable it for all other machines.
PowerPC has no remainder instruction; the back end uses division to
compute remainder. If CS finds both a / b and a % b, then CS now
rewrites a % b as a - b * (a / b) and computes a / b only once. This
removes an extra division in the PowerPC code, so it saves both time
and space.
I have not considered whether to enable this optimization for other
machines. It might be less useful in machines with a remainder
instruction. Also, if a % b occurs before a / b, the EM code gets a
DUP. PowerPC ncg handles this DUP well; other back ends might not.
This uncovers a problem in il/il_aux.c: it passes 3 arguments to
getlines(), but the function expects 4 arguments. I add FALSE as the
4th argument. TRUE would fill in the list of mesregs. IL uses
mesregs during phase 1, but this call to getlines() is in phase 2.
TRUE would leak memory unless I added a call to Ldeleteset(mesregs).
So I pass FALSE.
Functions passed to go() now have a `void *` parameter because
no_action() now takes a `void *`.
