Log Message:
Update to 1.20.0:

Changes in version 1.20.0:
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*
*Add "si" (Sinhala) to ALL_LINGUAS.

Changes in version 1.19.6:
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*
*Fixes #460851. Add a new API: atk_get_version.

Changes in version 1.19.3:
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*
*Fixes #434784.
*Remove gnome-doc-utils dependence.

Changes in version 1.19.1:
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*
*Fixes #382328, #418194, #413357.