+/* Declaration status of a symbol.
+
+ First, it is "undeclared". Then, if "undeclared" and used in a
+ %printer/%destructor, it is "used". If not "declared" by used in a
+ rule, it is "needed". Finally, if declared (via a rule for
+ nonterminals, or %oken), it is "declared".
+
+ When status are checked at the end, "declared" symbols are fine,
+ "used" symbols trigger warnings, otherwise it's an error.
+*/
+