Added #includes needed for ppc64 port. Renamed _MODEL_ppc to _MODEL_ppc_32 and renamed corresponding old _ppc files to _ppc_32.
Reviewed-by: dholmes, kvn
Distinguish PPC, PPC64 and PPC32. PPC should guard code needed on any PPC system. PPC32 and PPC64 should guard code needed in a port for the ppc64 or ppc32 instruction set.
Reviewed-by: kvn