Merge lowerCall and lowerRet between x86 and x64

src/IceTargetLoweringX8664.h

Index: src/IceTargetLoweringX8664.h
diff --git a/src/IceTargetLoweringX8664.h b/src/IceTargetLoweringX8664.h
index 0f8722b93ed5d2c1cb8cd96b464a028dc39c848b..e10d8345ec0a829cf6965f71860cae1c7c324023 100644
--- a/src/IceTargetLoweringX8664.h
+++ b/src/IceTargetLoweringX8664.h
@@ -60,9 +60,8 @@ protected:
 
   void initSandbox();
   void lowerIndirectJump(Variable *JumpTarget);
-  void lowerCall(const InstCall *Instr) override;
-  void lowerArguments() override;
-  void lowerRet(const InstRet *Inst) override;
+  Inst *emitCallToTarget(Operand *CallTarget, Variable *ReturnReg) override;
+  Variable *moveReturnValueToRegister(Operand *Value, Type ReturnType) override;
   void addProlog(CfgNode *Node) override;
   void addEpilog(CfgNode *Node) override;