Log Message:
atk: updated to 2.38.0

Changes in version 2.38
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* Require Meson 0.56.2
* Add g_autoptr support for ATK types
* Add ATK_STATE_COLLAPSED, matching AT-SPI's state
* Improve support for ATK as a Meson subproject
* Ensure that atk_value_get_value_and_text() can deal with NULL out arguments