At-spi2-core 2.56 has the needed support to utilize the org.freedesktop.a11y.KeyboardMonitor interface for reporting keyboard events.

We want to utilize it for Orca, as it will make the user experience much more consistent with what visually impaired users expect.

Because there were only a handful of other changes (mainly bug fixes), a rebase seems as the more straight-forward course of action for this package.