JAZZ 82314 - V8 - PPC simulation mode - failures in fround

Some of the unit tests were failing in ppc simulation mode.  Turned out
we had not fully implemented FRSP.  See JAZZ 82314 for more details

	modified:   src/ppc/simulator-ppc.cc
Cleanup for contribution back to google - native simulation

We won't be contributing back the code for native simulation but at the
same time we don't want to delete it from our code base.  This
commit fixes up some defines so they are guarded by the native simulation
option as they should be and organizes other so that the simulation
feature can be easily remove with the sunifdef tool

	modified:   src/assembler.cc
	modified:   src/assembler.h
	modified:   src/isolate.h