util.iterators: Use table.pack() on Lua 5.2

util/iterators.lua

@@ -13,7 +13,7 @@ local it = {};
 local t_insert = table.insert;
 local select, next = select, next;
 local unpack = table.unpack or unpack; --luacheck: ignore 113
-local function pack(...) return { n = select("#", ...), ... }; end
+local pack = table.pack or function (...) return { n = select("#", ...), ... }; end
 
 -- Reverse an iterator
 function it.reverse(f, s, var)