New show product

This is the human-readable buddy of xdump product, which dumps pchr[].
It duplicates much of the information in show sect c, but in more
accessible form.  It's in show_product().

Remove product information from info Quick-ref.  show reflects the
actual game, is more complete, and should be just as readable.

src/lib/commands/show.c

@@ -98,6 +98,10 @@ show(void)
 	cfunc = show_land_capab;
 	break;
     case 'p':
+	if (p[1] == 'r') {
+	    show_product(99999);
+	    return RET_OK;
+	}
 	bfunc = show_plane_build;
 	sfunc = show_plane_stats;
 	cfunc = show_plane_capab;