Kill GCC warnings.

* src/reduce.c (nonterminals_reduce): Don't loop over RITEM: loop
over the RHS of each rule.
* src/gram.h, src/gram.c (nritems): Is `unsigned int', not int.
* src/state.h (state_t): Member `nitems' is unsigned short.
* src/LR0.c (get_state): Adjust.
* src/reader.c (packgram): Likewise.
* src/output.c (GENERATE_MUSCLE_INSERT_TABLE): `max' is of type
`Type'.
(muscle_insert_int_table): Remove, unused.
(prepare_rules): Remove `max'.

src/state.h

@@ -185,7 +185,7 @@ typedef struct state_s
   int nlookaheads;
 
   /* Its items. */
-  short nitems;
+  unsigned short nitems;
   item_number_t items[1];
 } state_t;