gio: Add source tags to various GTasks constructed in GLib

This makes them easier to identify when debugging and profiling.

This patch was somewhat less than interesting to write.

https://bugzilla.gnome.org/show_bug.cgi?id=767765

gio/gsocketconnection.c

@@ -196,6 +196,7 @@ g_socket_connection_connect_async (GSocketConnection   *connection,
   g_return_if_fail (G_IS_SOCKET_ADDRESS (address));
 
   task = g_task_new (connection, cancellable, callback, user_data);
+  g_task_set_source_tag (task, g_socket_connection_connect_async);
 
   g_socket_set_blocking (connection->priv->socket, FALSE);
 
@@ -501,6 +502,7 @@ g_socket_connection_close_async (GIOStream           *stream,
   class = G_IO_STREAM_GET_CLASS (stream);
 
   task = g_task_new (stream, cancellable, callback, user_data);
+  g_task_set_source_tag (task, g_socket_connection_close_async);
 
   /* socket close is not blocked, just do it! */
   error = NULL;