Lua API: Add wesnoth.sides.iter

This replaces both helper.get_sides and helper.all_teams

data/lua/core/sides.lua

@@ -16,6 +16,20 @@ if wesnoth.kernel_type() == "Game Lua Kernel" then
 		end
 	}
 	setmetatable(wesnoth.sides, sides_mt)
+
+	function wesnoth.sides.iter(filter)
+		local function f(s)
+			local i = s.i
+			while i < #wesnoth.sides do
+				i = i + 1
+				if filter == nil or wesnoth.sides.matches(i, filter) then
+					s.i = i
+					return wesnoth.sides[i], i
+				end
+			end
+		end
+		return f, { i = 0 }
+	end
 
 	-- Deprecated functions
 	function wesnoth.set_side_variable(side, var, val)

data/lua/helper.lua

@@ -112,5 +112,7 @@ helper.get_user_choice = wesnoth.deprecate_api('helper.get_user_choice', 'gui.ge
 helper.rand = wesnoth.deprecate_api('helper.rand', 'mathx.random_choice', 1, nil, mathx.random_choice)
 helper.round = wesnoth.deprecate_api('helper.round', 'mathx.round', 1, nil, mathx.round)
 helper.shuffle = wesnoth.deprecate_api('helper.shuffle', 'mathx.shuffle', 1, nil, mathx.shuffle)
+helper.all_teams = wesnoth.deprecate_api('helper.all_teams', 'wesnoth.sides.iter', 1, nil, helper.all_teams)
+helper.get_sides = wesnoth.deprecate_api('helper.get_sides', 'wesnoth.sides.iter', 1, nil, helper.get_sides)
 
 return helper