Log Message:
Update at-spi2-core to 2.16.0

* Fix a couple of gtk-doc warnings (fdo#89678).
* Deprecate atspi_text_get_text_{before,at,after}_offset() (bgo#697969)
* Add roles for fractions, roots, subscripts, and superscripts (bgo#743403).
* Add names to every timeout (bgo#710644).
* Remove accessibility.conf from EXTRA_DIST (bgo#742987).
* Add ATSPI_STATE_READONLY (bgo#690004).
* Replace deprecated "Rename to" gtk-doc tag.
* Fix atspi_table_cell_get_column_span prototype.
* Make the documentation of ATSPI's STATE_ACTIVE consistent with that of
  ATK's (bgo#740274).
* Add ATSPI_ROLE_STATIC and update documentation for ATSPI_ROLE_TEXT
  (bgo#740340).
* gi-annotations: get_relation_set returns a array of AtspiRelation
* Fix some issues with the accessibility bus configuration (bgo#722738).
* Documentation for AtspiTableCell is now built.