bytecode: do not trim cps regs.
bytecode: do not trim cps regs.

the VM saves and restores registers contiguously, so we can't pick and
  choose registers from the middle to not bother saving/restoring.
  I don't think the gains from trimming them will offset the added
  complexity (and code size) of specifying full sets to save/restore.

samrushing/irken-compiler,samrushing/irken-compiler,samrushing/irken-compiler,samrushing/irken-compiler