[test] add missing header for the test.

llvm-svn: 180719
diff --git a/clang/test/Preprocessor/pp-modules.h b/clang/test/Preprocessor/pp-modules.h
new file mode 100644
index 0000000..e4ccacf
--- /dev/null
+++ b/clang/test/Preprocessor/pp-modules.h
@@ -0,0 +1 @@
+#include <Module/Module.h>