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>.

llvm-svn: 266808
diff --git a/libcxx/test/std/utilities/utility/synopsis.pass.cpp b/libcxx/test/std/utilities/utility/synopsis.pass.cpp
new file mode 100644
index 0000000..edb45cf
--- /dev/null
+++ b/libcxx/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;
+}
+