supress undeclared variable access warnings in cases of intentional declaration checks

concrete/init.lua

@@ -1,12 +1,12 @@
 --Minetest 0.4.7 mod: concrete 
 --(c) 2013 by RealBadAngel <mk@realbadangel.pl>
 
-local technic = technic or {}
+local technic = rawget(_G, "technic") or {}
 technic.concrete_posts = {}
 
 -- Boilerplate to support localized strings if intllib mod is installed.
 local S
-if intllib then
+if rawget(_G, "intllib") then
 	S = intllib.Getter()
 else
 	S = function(s) return s end