[C++] Correct the implementation of $*
diff --git a/strutil.h b/strutil.h
index caeb8de..5938efb 100644
--- a/strutil.h
+++ b/strutil.h
@@ -97,6 +97,8 @@
 
   bool Match(StringPiece str) const;
 
+  StringPiece Stem(StringPiece str) const;
+
   void AppendSubst(StringPiece str, StringPiece subst, string* out) const;
 
   void AppendSubstRef(StringPiece str, StringPiece subst, string* out) const;