Include initializer_list from utility

The C++11 and C++14 standards both say in the header <utility> synopsis that
<utility> shall include <initializer_list>.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@266808 91177308-0d34-0410-b5e6-96231b3b80d8

include/utility

@@ -178,6 +178,7 @@ template<class T, class U=T>
 #include <__config>
 #include <__tuple>
 #include <type_traits>
+#include <initializer_list>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header

test/std/utilities/utility/synopsis.pass.cpp

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <utility>
+
+// #include <initializer_list>
+
+#include <utility>
+
+int main()
+{
+    std::initializer_list<int> x;
+}
+