clang-format: Add comment to tests explaining their grouping.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190858 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index 3c29525..c5d0171 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -2069,6 +2069,8 @@
                    "    IPC_MESSAGE_HANDLER(xxx, qqq)\n"
                    "  IPC_END_MESSAGE_MAP()\n"
                    "}"));
+
+  // These must not be recognized as macros.
   EXPECT_EQ("int q() {\n"
             "  f(x);\n"
             "  f(x) {}\n"