[turbofan] Added the optional Float64RoundTiesEven operator to turbofan.

src/compiler/ppc/instruction-selector-ppc.cc

Index: src/compiler/ppc/instruction-selector-ppc.cc
diff --git a/src/compiler/ppc/instruction-selector-ppc.cc b/src/compiler/ppc/instruction-selector-ppc.cc
index 0e404a4a9b8597a1b0217c7bf3553cfd38d48103..46f9823186551659098024ac7ecab3f657a18670 100644
--- a/src/compiler/ppc/instruction-selector-ppc.cc
+++ b/src/compiler/ppc/instruction-selector-ppc.cc
@@ -1133,6 +1133,11 @@ void InstructionSelector::VisitFloat64RoundTiesAway(Node* node) {
 }
 
 
+void InstructionSelector::VisitFloat64RoundTiesEven(Node* node) {
+  UNREACHABLE();
+}
+
+
 void InstructionSelector::VisitInt32AddWithOverflow(Node* node) {
   if (Node* ovf = NodeProperties::FindProjection(node, 1)) {
     FlagsContinuation cont(kOverflow, ovf);