awful.titlebar: remove otable usage

Signed-off-by: Julien Danjou <julien@danjou.info>

lib/awful/titlebar.lua.in

@@ -8,7 +8,7 @@
 local math = math
 local image = image
 local pairs = pairs
-local otable = require("otable")
+local setmetatable = setmetatable
 local capi =
 {
     wibox = wibox,
@@ -27,7 +27,7 @@ local client = require("awful.client")
 module("awful.titlebar")
 
 -- Privata data
-local data = otable()
+local data = setmetatable({}, { __mode = 'k' })
 
 -- Predeclaration for buttons
 local button_groups
@@ -387,6 +387,5 @@ button_groups = { ontop_buttons,
 hooks.focus.register(update)
 hooks.unfocus.register(update)
 hooks.property.register(update)
-hooks.unmanage.register(remove)
 
 -- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=80