Use a single `intllib.Getter' for all the texts.

Just a minimal code reduction, but big reduction in code
duplication. This could help if in the future, support for
different "internationalization" mods will be added, or in
case Minetest supports I18N/L10N internally in the engine.

lighting.lua

@@ -1,14 +1,7 @@
 
 -- This file supplies glowlights
 
--- Boilerplate to support localized strings if intllib mod is installed.
-local S
-if homedecor.intllib_modpath then
-    dofile(homedecor.intllib_modpath.."/intllib.lua")
-    S = intllib.Getter(minetest.get_current_modname())
-else
-    S = function ( s ) return s end
-end
+local S = homedecor.gettext
 
 local colors = {"yellow","white"}