API show if pool has GBT (so people know not to use that pool)

api.c

@@ -1977,6 +1977,7 @@ static void poolstatus(struct io_data *io_data, __maybe_unused SOCKETTYPE c, __m
 			root = api_add_escape(root, "Stratum URL", pool->stratum_url, false);
 		else
 			root = api_add_const(root, "Stratum URL", BLANK, false);
+		root = api_add_bool(root, "Has GBT", &(pool->has_gbt), false);
 
 		root = print_data(root, buf, isjson, isjson && (i > 0));
 		io_add(io_data, buf);