require improvements, remove global Util

sys/extensions/tl3.lua

@@ -2,6 +2,10 @@ if not turtle then
   return
 end
 
+requireInjector(getfenv(1))
+
+local Util = require('util')
+
 local function noop() end
 
 turtle.point = { x = 0, y = 0, z = 0, heading = 0 }