wibox: Remove weak table hack

No idea what self referencing loops this refers to. Lua 5.1's and
LuaJIT's garbage collector both should handle cycles just fine. Things
only start getting complicated when you start using weak tables.

Unless someone comes up with an example where this patch causes a leak,
let's remove the weak table magic.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/wibox/init.lua

@@ -158,11 +158,8 @@ local function new(args)
     local ret = object()
     local w = capi.drawin(args)
 
-    -- lua 5.1 and luajit have issues with self referencing loops
-    local avoid_leak = setmetatable({ret},{__mode="v"})
-
     function w.get_wibox()
-        return avoid_leak[1]
+        return ret
     end
 
     ret.drawin = w