c2hal: Comment out lone declarations.

Test: `make c2hal` and examine the result for c2hal/test/test.h

Change-Id: I1a72ecaddf6215b94bd76f3e8b09ed6def9aadcc
diff --git a/c2hal/Note.h b/c2hal/Note.h
index 7870191..ebdcd49 100644
--- a/c2hal/Note.h
+++ b/c2hal/Note.h
@@ -30,6 +30,8 @@
  */
 struct Note : Declaration {
     Note(const std::string &name);
+    // assume ownership on decl
+    Note(Declaration *decl);
     ~Note();
 
     static std::string type() { return "note"; }
@@ -39,7 +41,7 @@
     void processContents(AST &ast) override;
 
 private:
-    std::string mExpression;
+    Declaration *mDecl = nullptr;
 
     DISALLOW_COPY_AND_ASSIGN(Note);
 };