MS ABI: Define _HAS_CHAR16_T_LANGUAGE_SUPPORT when appropriate

If we are in MSVC 2015 compatibility mode and C++11 language conformance
is enabled, define _HAS_CHAR16_T_LANGUAGE_SUPPORT to 1.

llvm-svn: 232615
diff --git a/clang/test/SemaCXX/MicrosoftCompatibility.cpp b/clang/test/SemaCXX/MicrosoftCompatibility.cpp
index 480c7cb..1536007 100644
--- a/clang/test/SemaCXX/MicrosoftCompatibility.cpp
+++ b/clang/test/SemaCXX/MicrosoftCompatibility.cpp
@@ -1,13 +1,17 @@
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 -Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions -fms-compatibility-version=19.00
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -std=c++11 -Wmicrosoft -verify -fms-compatibility -fexceptions -fcxx-exceptions -fms-compatibility-version=18.00
 
-#if _MSC_VER >= 1900
+#if defined(_HAS_CHAR16_T_LANGUAGE_SUPPORT) && _HAS_CHAR16_T_LANGUAGE_SUPPORT
 char16_t x;
 char32_t y;
-_Atomic(int) z;
 #else
 typedef unsigned short char16_t;
 typedef unsigned int char32_t;
+#endif
+
+#if _MSC_VER >= 1900
+_Atomic(int) z;
+#else
 struct _Atomic {};
 #endif