Refactored include diagram visitors

src/util/util.cc

@@ -230,5 +230,10 @@ bool starts_with(
     return pref == pat;
 }
 
+template <> bool starts_with(const std::string &s, const std::string &prefix)
+{
+    return s.rfind(prefix, 0) == 0;
+}
+
 }
 }