Changed 'unreferenced rule' not to be reported as error, but warning

peglib.h

@@ -3677,7 +3677,6 @@ private:
           auto msg = "'" + name + "' is not referenced.";
           log(line.first, line.second, msg);
         }
-        ret = false;
       }
     }
 

test/test2.cc

@@ -1112,7 +1112,7 @@ TEST_CASE("Unreferenced rule", "[macro]") {
 	)");
 
   bool ret = parser;
-  REQUIRE(ret == false);
+  REQUIRE(ret == true); // This is OK, because it's a warning, not an erro...
 }
 
 TEST_CASE("Nested macro call", "[macro]") {