add NetWatcher thread

This deals with interruptions in network connectevity, by listening
for a new network interface coming up (using dbus to see when
network-manager or wicd do it), and forcing a rescan of

Utility/DBus.hs

@@ -0,0 +1,28 @@
+{- DBus utilities
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# LANGUAGE OverloadedStrings #-}
+
+module Utility.DBus where
+
+import DBus.Client
+import DBus
+import Data.Maybe
+
+type ServiceName = String
+
+listServiceNames :: Client -> IO [ServiceName]
+listServiceNames client = do
+	reply <- callDBus client "ListNames" []
+	return $ fromMaybe [] $ fromVariant (methodReturnBody reply !! 0)
+
+callDBus :: Client -> MemberName -> [Variant] -> IO MethodReturn
+callDBus client name params = call_ client $
+	(methodCall "/org/freedesktop/DBus" "org.freedesktop.DBus" name)
+		{ methodCallDestination = Just "org.freedesktop.DBus"
+		, methodCallBody = params
+		}