[turbofan] Use correct CEntryStub according to function's result size.

The code generated for this stub may differ based on the result size
on certain platforms (e.g. 64-bit BE Linux and AIX).

Conflicts:

	src/compiler/js-generic-lowering.cc
	src/compiler/js-generic-lowering.h
[turbofan] Add turbofan support for PPC.

Conflicts:

	src/ppc/code-stubs-ppc.cc
	src/test/test.gyp
	tools/gyp/v8.gyp
PPC: turbofan changes [08b12bb..2f0cfa9]