Implement the infrastructure for feature-test macros. Very few actual feature test macros, though. Reviewed as: https://reviews.llvm.org/D51955

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@342073 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/language.support/support.limits/support.limits.general/cmath.version.pass.cpp

@@ -0,0 +1,33 @@
+
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+//
+// <cmath> feature macros
+
+/*  Constant                                    Value
+    __cpp_lib_hypot                             201603L
+    __cpp_lib_math_special_functions            201603L
+
+*/
+
+#include <cmath>
+#include "test_macros.h"
+
+int main()
+{
+//  ensure that the macros that are supposed to be defined in <cmath> are defined.
+
+/*
+#if !defined(__cpp_lib_fooby)
+# error "__cpp_lib_fooby is not defined"
+#elif __cpp_lib_fooby < 201606L
+# error "__cpp_lib_fooby has an invalid value"
+#endif
+*/
+}