Refactor all instances of `typedef y x` to the C++11 `using x = y` syntax.

src/IceTargetLoweringX8664Traits.h

Index: src/IceTargetLoweringX8664Traits.h
diff --git a/src/IceTargetLoweringX8664Traits.h b/src/IceTargetLoweringX8664Traits.h
index 2caaeb5524d6bf38669984307f3ab776d30811d3..454b6cb82d214acf1a9c719c9b0994bf911a8e1b 100644
--- a/src/IceTargetLoweringX8664Traits.h
+++ b/src/IceTargetLoweringX8664Traits.h
@@ -410,8 +410,8 @@ template <> struct MachineTraits<TargetX8664> {
     // class.  For x86-64, this would comprise the 16 XMM registers.  This is
     // for performance, not correctness.
     static const unsigned MaxEquivalenceClassSize = 8;
-    typedef llvm::SmallVector<int32_t, MaxEquivalenceClassSize> RegisterList;
-    typedef std::map<uint32_t, RegisterList> EquivalenceClassMap;
+    using RegisterList = llvm::SmallVector<int32_t, MaxEquivalenceClassSize>;
+    using EquivalenceClassMap = std::map<uint32_t, RegisterList>;
     EquivalenceClassMap EquivalenceClasses;
     SizeT NumShuffled = 0, NumPreserved = 0;