Add LLVM_HAS_INITIALIZER_LISTS for upcoming C++11 support. Use it in ArrayRef

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194362 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/ArrayRef.h

@@ -83,6 +83,13 @@ namespace llvm {
     /*implicit*/ LLVM_CONSTEXPR ArrayRef(const T (&Arr)[N])
       : Data(Arr), Length(N) {}
 
+#if LLVM_HAS_INITIALIZER_LISTS
+    /// Construct an ArrayRef from a std::initializer_list.
+    /*implicit*/ ArrayRef(const std::initializer_list<T> &Vec)
+    : Data(Vec.begin() == Vec.end() ? (T*)0 : Vec.begin()),
+      Length(Vec.size()) {}
+#endif
+
     /// @}
     /// @name Simple Operations
     /// @{