Replace deprecated function 'intllib.Getter':

- Check first for 'intllib.make_gettext_pair', otherwise continue using
old function.

init.lua

@@ -7,7 +7,13 @@ ilights = {}
 -- Boilerplate to support localized strings if intllib mod is installed.
 local S
 if minetest.global_exists("intllib") then
+	if intllib.make_gettext_pair then
+		-- New method using gettext.
+		S = intllib.make_gettext_pair()
+	else
+		-- Old method using text files.
 		S = intllib.Getter()
+	end
 else
 	S = function(s) return s end
 end