Rewrite minimization-related modules

* Use global state instead of per-layout - so now window is minimized on
  all workspaces (EWMH requires that windows with _NET_WM_STATE_HIDDEN
  set should be minimized on any workspace but previously they were not)
* Use `windows` instead of `modify`. That should fix bugs related to
  actions that should be done by `windows` and not done by
  `modify` (fixes #46)
* Mark module X.H.RestoreMinimized as deprecated

XMonad/Util/Minimize.hs

@@ -0,0 +1,37 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+----------------------------------------------------------------------------
+-- |
+-- Module      :  XMonad.Util.Minimize
+-- Copyright   :  (c) Bogdan Sinitsyn (2016)
+-- License     :  BSD3-style (see LICENSE)
+--
+-- Maintainer  :  bogdan.sinitsyn@gmail.com
+-- Stability   :  unstable
+-- Portability :  not portable
+--
+-- Stores some common utilities for modules used for window minimizing/maximizing
+--
+-----------------------------------------------------------------------------
+module XMonad.Util.Minimize
+  ( RectMap
+  , Minimized(..)
+  ) where
+
+import XMonad
+import qualified XMonad.StackSet as W
+
+import qualified Data.Map as M
+
+type RectMap = M.Map Window (Maybe W.RationalRect)
+
+data Minimized = Minimized
+    { rectMap :: RectMap
+    , minimizedStack :: [Window]
+    }
+    deriving (Eq, Typeable, Read, Show)
+
+instance ExtensionClass Minimized where
+  initialValue = Minimized { rectMap = M.empty
+                           , minimizedStack = []
+                           }
+  extensionType = PersistentExtension