awful.tooltip: add "delay_show" arg

This will wrap the show and hide methods using gears.timeout.

lib/awful/tooltip.lua.in

@@ -164,6 +164,8 @@ end
 -- @tparam function args.timer_function A function to dynamically change the
 --                                      tooltip text.
 -- @tparam table    args.objects A list of objects linked to the tooltip.
+-- @tparam number   args.delay_show Delay showing the tooltip by this many
+--                                  seconds.
 -- @return The created tooltip.
 -- @see add_to_object
 -- @see set_timeout
@@ -176,9 +178,20 @@ tooltip.new = function(args)
     }
 
     -- private data
+    local delay_timeout
+    if args.delay_show then
+        delay_timeout = timer { timeout = args.delay_show }
+        delay_timeout:connect_signal("timeout", function () show(self) end)
+    end
     data[self] = {
-        show = function() show(self) end,
+        show = function()
-        hide = function() hide(self) end
+            if delay_timeout then delay_timeout:start()
+            else show(self) end
+        end,
+        hide = function()
+            if delay_timeout then delay_timeout:stop() end
+            hide(self)
+        end,
     }
 
     -- export functions