Fix bugs in PPC.Instr.allocMoreStack (#7498)

This patch is ported from #7510, which fixes the same bug in the x86 nativeGen.
Merge remote-tracking branch 'phonohawk/ticket-7498'

* phonohawk/ticket-7498:
  Fix bugs in PPC.Instr.allocMoreStack (#7498)
allocMoreStack: we should be retargetting table jumps too.

Thanks to @PHO on #7498 for pointing this out.