PPC: [Interpreter] Add ForInPrepare runtime function which returns a ObjectTriple.

src/ppc/macro-assembler-ppc.h

Index: src/ppc/macro-assembler-ppc.h
diff --git a/src/ppc/macro-assembler-ppc.h b/src/ppc/macro-assembler-ppc.h
index 78de89aa5c64b1d87d1728e53d4663e7bd1e1f37..2c842f828fba943a916f2f9bcc82aed7934e5e6f 100644
--- a/src/ppc/macro-assembler-ppc.h
+++ b/src/ppc/macro-assembler-ppc.h
@@ -16,6 +16,7 @@ namespace internal {
 // Give alias names to registers for calling conventions.
 const Register kReturnRegister0 = {Register::kCode_r3};
 const Register kReturnRegister1 = {Register::kCode_r4};
+const Register kReturnRegister2 = {Register::kCode_r5};
 const Register kJSFunctionRegister = {Register::kCode_r4};
 const Register kContextRegister = {Register::kCode_r30};
 const Register kInterpreterAccumulatorRegister = {Register::kCode_r3};