Log Message:
Update at-spi2-core to 2.20.2

What's new in at-spi2-core 2.20.2:

* Fixed an invalid memory access when fetching an accessible..

What's new in at-spi2-core 2.20.1:

* registryd: avoid crashing with a NULL keystring (bgo#764688).
* Plug a memory leak in AtspiEventListener (bgo#764688).