(deli, do_demo, lnd_sweep, guerrilla): Saturate items at ITEM_MAX.

With variables, item increases beyond the capacity of variables
(65535) were ignored here.

This should cover all item changes not going through putvec().

src/lib/commands/deli.c

@@ -101,7 +101,8 @@ deli(void)
 	    if (!check_sect_ok(&sect))
 		continue;
 
-	    del = thresh + dir;
+	    thresh = min(thresh, ITEM_MAX) & ~7;
+	    del = thresh | dir;
 	    sect.sct_del[ich->i_vtype] = del;
 	    putsect(&sect);
 	}