style: make item_index a truly different type from item_number

See previous commit.

* src/gram.h (item_index): Make it unsigned.
Fix remaiming issues.

src/closure.c

@@ -60,10 +60,10 @@ closure_print (char const *title, item_index const *array, size_t size)
   for (size_t i = 0; i < size; ++i)
     {
       fprintf (stderr, "  %2d: .", array[i]);
-      item_index *rp;
-      for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
+      item_number *rp;
+      for (rp = &ritem[array[i]]; 0 <= *rp; ++rp)
         fprintf (stderr, " %s", symbols[*rp]->tag);
-      fprintf (stderr, "  (rule %d)\n", -*rp - 1);
+      fprintf (stderr, "  (rule %d)\n", item_number_as_rule_number (*rp));
     }
   fputs ("\n\n", stderr);
 }

src/gram.h

@@ -111,14 +111,15 @@ extern int nsyms;
 extern int ntokens;
 extern int nvars;
 
-/* elements of ritem */
+/* Elements of ritem. */
 typedef int item_number;
-/* indices into ritem */
-typedef int item_index;
 # define ITEM_NUMBER_MAX INT_MAX
 extern item_number *ritem;
 extern int nritems;
 
+/* Indices into ritem. */
+typedef unsigned int item_index;
+
 /* There is weird relationship between OT1H item_number and OTOH
    symbol_number and rule_number: we store the latter in
    item_number.  symbol_number values are stored as-is, while

src/ielr.c

@@ -1030,7 +1030,7 @@ ielr_split_states (bitsetv follow_kernel_items, bitsetv always_follows,
         if (!node->state->consistent)
           {
             size_t i = 0;
-            item_number *itemset = node->state->items;
+            item_index *itemset = node->state->items;
             for (size_t r = 0; r < node->state->reductions->num; ++r)
               {
                 rule *this_rule = node->state->reductions->rules[r];

src/print-xml.c

@@ -57,7 +57,7 @@ static struct escape_buf escape_bufs[num_escape_bufs];
 static void
 print_core (FILE *out, int level, state *s)
 {
-  item_number *sitems = s->items;
+  item_index *sitems = s->items;
   size_t snritems = s->nitems;
 
   /* Output all the items of a state, not only its kernel.  */

src/print.c

@@ -61,7 +61,7 @@ max_length (size_t *width, const char *str)
 static void
 print_core (FILE *out, state *s)
 {
-  item_number *sitems = s->items;
+  item_index *sitems = s->items;
   size_t snritems = s->nitems;
   /* Output all the items of a state, not only its kernel.  */
   if (report_flag & report_itemsets)