Log Message:
Update to at-spi2-atk 2.5.4

* Fix for bug #679013 - AtspiCollection should be implemented for
  all containers
* Plug ref count leaks (BGO#679285).
* Only add items to the cache on children-changed if the children are
  included in the event.
* Only send PropertyChange signals used for caching, absent listeners.

Especially:

* Only create a directory and a socket when requested.
    Currently, atk-bridge clutters XDG_RUNTIME_DIR with directories for sockets,
    which is especially annoying since gtk currently does not call
    atk_bridge_adaptor_cleanup, so the directories never go away. This change do
    not really solve the problem--it only hides it from users who do not really
    need AT-SPI--but, nevertheless, there is no reason to create a directory or
    socket if nothing has requested it, so doing this lazily makes sense.

* Don't create a (non-readable) subdirectory for the socket when root.
    If an application is running as root but within a user's runtime directory,
    then creating a temporary directory will result in the directory being owned
    by root, and the user will not have permission to search the directory to
    access the socket, so an AT running as the normal user will not be able to
    connect to the application running as root.
    Fixes regression introduced by the fix for BGO#678348.