Implement a Telepathy Approver and Handler (#643594)

As the Shell does more than observing channels (users can interact with them),
it has to be an Handler as well. We have to make sure that all the new
incoming text channels are handled by the Shell by default, so we make it an
Approver as well.

From an user point of view, the only difference is that Empathy's tray icon
will stop blicking when receiving new channels.

We rely on ChannelDispatcher.DelegateChannels() and PresentChannel() to
interact with Empathy. Those methods have been implemented in
telepathy-mission-control 5.9.0 and telepathy-glib 0.15.0.

src/shell-tp-client.h

@@ -51,13 +51,40 @@ typedef void (*ShellTpClientObserveChannelsImpl) (ShellTpClient *client,
                                                   TpObserveChannelsContext *context,
                                                   gpointer user_data);
 
-ShellTpClient * shell_tp_client_new (TpDBusDaemon *dbus);
-
 void shell_tp_client_set_observe_channels_func (ShellTpClient *self,
                                                 ShellTpClientObserveChannelsImpl observe_impl,
                                                 gpointer user_data,
                                                 GDestroyNotify destroy);
 
+typedef void (*ShellTpClientApproveChannelsImpl) (
+    ShellTpClient *client,
+    TpAccount *account,
+    TpConnection *connection,
+    GList *channels,
+    TpChannelDispatchOperation *dispatch_operation,
+    TpAddDispatchOperationContext *context,
+    gpointer user_data);
+
+void shell_tp_client_set_approve_channels_func (ShellTpClient *self,
+    ShellTpClientApproveChannelsImpl approve_impl,
+    gpointer user_data,
+    GDestroyNotify destroy);
+
+typedef void (*ShellTpClientHandleChannelsImpl) (
+    ShellTpClient *client,
+    TpAccount *account,
+    TpConnection *connection,
+    GList *channels,
+    GList *requests_satisfied,
+    gint64 user_action_time,
+    TpHandleChannelsContext *context,
+    gpointer user_data);
+
+void shell_tp_client_set_handle_channels_func (ShellTpClient *self,
+    ShellTpClientHandleChannelsImpl handle_channels_impl,
+    gpointer user_data,
+    GDestroyNotify destroy);
+
 /* Telepathy utility functions */
 typedef void (*ShellGetTpContactCb) (TpConnection *connection,
                                      GList *contacts,