Warn about unused values.

* src/symlist.h, src/symlist.c (symbol_list, symbol_list_new): Add
a `used' member.
(symbol_list_n_get, symbol_list_n_used_set): New.
(symbol_list_n_type_name_get): Use symbol_list_n_get.
* src/scan-gram.l (handle_action_dollar): Flag used symbols.
* src/reader.c (grammar_current_rule_check): Check that values are
used.
* src/symtab.c (symbol_print): Accept 0.
* tests/existing.at: Remove the type information.
Empty the actions.
Remove useless actions (beware of mid-rule actions: perl -000
-pi -e 's/s*{}(?=[ns]*[|;])//g').
* tests/actions.at (Exotic Dollars): Use unused values.
* tests/calc.at: Likewise.
* tests/glr-regression.at (No users destructors if stack 0 deleted):
Likewise.
* src/gram.c (rule_useful_p, rule_never_reduced_p): Use
rule_useful_p.

src/gram.c

@@ -65,7 +65,7 @@ rule_useful_p (rule *r)
 bool
 rule_useless_p (rule *r)
 {
-  return r->number >= nrules;
+  return !rule_useful_p (r);
 }
 
 
@@ -77,7 +77,7 @@ rule_useless_p (rule *r)
 bool
 rule_never_reduced_p (rule *r)
 {
-  return !r->useful && r->number < nrules;
+  return !r->useful && rule_useful_p (r);
 }
 
 
@@ -317,8 +317,7 @@ grammar_rules_never_reduced_report (const char *message)
     if (!rules[r].useful)
       {
 	location_print (stderr, rules[r].location);
-	fprintf (stderr, ": %s: %s: ",
-		 _("warning"), message);
+	fprintf (stderr, ": %s: %s: ", _("warning"), message);
 	rule_print (&rules[r], stderr);
       }
 }