Allow GlobalEntityList to be iterated by pairs and ipairs

* See 6309529590

Example usage:

for ent_id, ent in pairs(GlobalEntityList) do
  print(ent_id, ent)
end

Note: The order of iteration is always arbitrary

maps/includes/base.lua

@@ -49,6 +49,47 @@ function baseclass:new (o)
 end
 
 
+-----------------------------------------------------------------------------
+-- set up pairs and ipairs for iterating the global entity list
+--
+-- Example usage:
+--
+--   for ent_id, ent in pairs(GlobalEntityList) do
+--     print(ent_id, ent)
+--   end
+--
+-- Note: The order of iteration is always arbitrary
+-----------------------------------------------------------------------------
+local GlobalEntityListIterator = function()
+	local entity = GlobalEntityList:FirstEntity()
+	return function()
+		local cur_ent = entity
+		entity = GlobalEntityList:NextEntity(cur_ent)
+		if cur_ent then
+			return cur_ent:GetId(), cur_ent
+		else
+			return nil
+		end
+	end
+end
+
+local ipairs_base = ipairs
+ipairs = function(t)
+	if t == GlobalEntityList then
+		return GlobalEntityListIterator()
+	end
+	return ipairs_base(t)
+end
+
+local pairs_base = pairs
+pairs = function(t)
+	if t == GlobalEntityList then
+		return GlobalEntityListIterator()
+	end
+	return pairs_base(t)
+end
+
+
 -----------------------------------------------------------------------------
 -- make luabind's class_info function safer
 -- (don't crash if class_info() is called on non-luabind objects)