Replace __cplusplus comparisons and dialect __has_feature checks with TEST_STD_VER.

This is a huge cleanup that helps make the libc++ test suite more portable.
Patch from STL@microsoft.com. Thanks STL!


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@272716 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/thread/thread.mutex/thread.once/thread.once.callonce/call_once.pass.cpp

@@ -21,6 +21,8 @@
 #include <thread>
 #include <cassert>
 
+#include "test_macros.h"
+
 typedef std::chrono::milliseconds ms;
 
 std::once_flag flg0;
@@ -171,7 +173,7 @@ public:
     void operator()(int&) {}
 };
 
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
 // reference qualifiers on functions are a C++11 extension
 struct RefQual
 {
@@ -240,7 +242,7 @@ int main()
         int i = 0;
         std::call_once(f, NonCopyable(), i);
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
 // reference qualifiers on functions are a C++11 extension
     {
         std::once_flag f1, f2;