Introduce __has_feature(attribute_unused_on_fields) to determine whether
the current version of clang understands __attribute__((unused)) on
fields.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159252 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/SemaCXX/warn-unused-member.cpp b/test/SemaCXX/warn-unused-member.cpp
index cabc9b6..6a7922e 100644
--- a/test/SemaCXX/warn-unused-member.cpp
+++ b/test/SemaCXX/warn-unused-member.cpp
@@ -144,6 +144,13 @@
   int by_initializer_;
 };
 
+class HasFeatureTest {
+#if __has_feature(attribute_unused_on_fields)
+  int unused_; // expected-warning{{private field 'unused_' is not used}}
+  int unused2_ __attribute__((unused)); // no-warning
+#endif
+};
+
 namespace templates {
 class B {
   template <typename T> void f(T t);