Revert "restart when number of screens changes"

This reverts commit 3c90d4d.

This causes a fork bomb when running the qtile tests. I don't understand why,
but putting other code here (specifically, firing hooks) seems to cause
problems too. More to come later...

libqtile/manager.py

@@ -1374,9 +1374,6 @@ def handle_UnmapNotify(self, e):
         if e.event != self.root.wid:
             self.unmanage(e.window)
 
-    def handle_ScreenChangeNotify(self, e):
-        self.cmd_restart()
-
     def toScreen(self, n):
         """
         Have Qtile move to screen and put focus there

libqtile/xcbq.py

@@ -261,10 +261,6 @@ def query_screens(self):
 class RandR:
     def __init__(self, conn):
         self.ext = conn.conn(xcb.randr.key)
-        self.ext.SelectInput(
-            conn.default_screen.root.wid,
-            xcb.randr.NotifyMask.ScreenChange
-        )
 
     def query_crtcs(self, root):
         l = []
@@ -673,12 +669,11 @@ def __init__(self, display):
         self.cursors = Cursors(self)
         self.setup = self.conn.get_setup()
         extensions = self.extensions()
-        self.screens = [Screen(self, i) for i in self.setup.roots]
-        self.default_screen = self.screens[self.conn.pref_screen]
         for i in extensions:
             if i in self._extmap:
                 setattr(self, i, self._extmap[i](self))
 
+        self.screens = [Screen(self, i) for i in self.setup.roots]
         self.pseudoscreens = []
         if "xinerama" in extensions:
             for i, s in enumerate(self.xinerama.query_screens()):
@@ -701,6 +696,7 @@ def __init__(self, display):
                 )
                 self.pseudoscreens.append(scr)
 
+        self.default_screen = self.screens[self.conn.pref_screen]
         self.atoms = AtomCache(self)
 
         self.code_to_syms = {}