Log Message:
Update at-spi2-atk to 2.20.0

* Don't drop the main context when p2p socket configuration fails
  (bgo#763273).
* Make sure the runtime directory exists (bgo#763274).
* Avoid lagging with large gtk menus (bgo#754048).
* Always accept connections as root if unable to find an owning user.
* Test fixes for atk-adaptor and cache changes.
* Fixes for Text, Value, and Table Cell adaptors (bgo#755724).
* Many new tests, thanks to Patryk Kaczmarek of Samsung.
* Update for new caching API (bgo#650090).
* Eliminate some console warnings due to NULL gobjects.
* Tests: fix out-of-source and parallel build (bgo#751137).
* Add some missing files to the distribution (bgo#751138).