Replace mesecon:<some_function> with mesecon.<some_function> for greater

flexibility and because it was never inteded to be OOP in the first
place.

mesecon.receptor_on and mesecon.receptor_off are provided by wrappers
(mesecon:receptor_on/off) for compatibility, but will be removed. Mod
programmers that use mesecons: Please update!

Also, fix microcontroller polluting the global namespace and remove some
deprecated stuff.

mesecons_switch/init.lua

@@ -11,7 +11,7 @@ minetest.register_node("mesecons_switch:mesecon_switch_off", {
 	}},
 	on_punch = function(pos, node)
 		minetest.swap_node(pos, {name = "mesecons_switch:mesecon_switch_on", param2 = node.param2})
-		mesecon:receptor_on(pos)
+		mesecon.receptor_on(pos)
 		minetest.sound_play("mesecons_switch", {pos=pos})
 	end
 })
@@ -27,7 +27,7 @@ minetest.register_node("mesecons_switch:mesecon_switch_on", {
 	}},
 	on_punch = function(pos, node)
 		minetest.swap_node(pos, {name = "mesecons_switch:mesecon_switch_off", param2 = node.param2})
-		mesecon:receptor_off(pos)
+		mesecon.receptor_off(pos)
 		minetest.sound_play("mesecons_switch", {pos=pos})
 	end
 })