master/slave: Also set the client property

My dynamic layout system is smarter than the old stateless system.
It can use this information when adding the client instead of
relying on the delayed call and dark index swapping magic.

init.lua

@@ -94,12 +94,18 @@ function awful.rules.delayed_properties.master(c, value)
     if not value then return end
 
     awful.client.setmaster(c)
+
+    -- Some smarter layouts may implement this directly
+    c.master = true
 end
 
 function awful.rules.delayed_properties.slave(c, value)
     if not value then return end
 
     awful.client.setslave(c)
+
+    -- Some smarter layouts may implement this directly
+    c.slave = true
 end
 
 function module.focus_client(c,properties)