Don't emit -Wunused-value warnings from macro expansions.

llvm-svn: 166522
diff --git a/clang/test/Sema/unused-expr.c b/clang/test/Sema/unused-expr.c
index 056d09a..6677e48 100644
--- a/clang/test/Sema/unused-expr.c
+++ b/clang/test/Sema/unused-expr.c
@@ -122,3 +122,10 @@
 
 // PR8371
 int fn5() __attribute__ ((__const));
+
+// OpenSSL has some macros like this.
+#define M(a, b) (long)foo((a), (b))
+void t11(int i, int j) {
+  M(i, j);  // no warning
+}
+#undef M