[C++] Fix patsubst.mk
diff --git a/strutil.h b/strutil.h
index f22bd40..7369787 100644
--- a/strutil.h
+++ b/strutil.h
@@ -31,6 +31,16 @@
   StringPiece in_;
 };
 
+class WordWriter {
+ public:
+  explicit WordWriter(string* o);
+  void Write(StringPiece s);
+
+ private:
+  string* out_;
+  bool needs_space_;
+};
+
 void InitSymtab();
 void QuitSymtab();
 StringPiece Intern(StringPiece s);