Introduce MoveDouble to the X64 MacroAssembler

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index d1c24343628d6f3d37e89c9b0a66b244875544d8..3e37e825bdfcd4d1c354d825ecb8794bec799bbb 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -846,6 +846,8 @@ class MacroAssembler: public Assembler {
   void Pop(Register dst) { pop(dst); }
   void PushReturnAddressFrom(Register src) { push(src); }
   void PopReturnAddressTo(Register dst) { pop(dst); }
+  void MoveDouble(Register dst, const Operand& src) { movq(dst, src); }
+  void MoveDouble(const Operand& dst, Register src) { movq(dst, src); }
 
   // Control Flow
   void Jump(Address destination, RelocInfo::Mode rmode);