enable accessibility on Linux when org.a11y.Status IsEnabled is true

enable accessibility on Linux when org.a11y.Status IsEnabled is true

Origin: upstream, https://code.qt.io/cgit/qt/qtbase.git/commit/?id=54886d7f81175ac6
Last-Update: 2020-04-16

Otherwise accessibility would only work when Orca is set to be started
in the session preference, and it would not work when running Orca or
compiz' zoom by hand.

The existing comment said that it was always true since gnome 3.6, but at
least in Debian 8's gnome 3.14, Debian 9's gnome 3.22, and Debian 10's
3.30 it is not always true, it is Orca which sets it on startup. Compiz's
focuspoll module also does so for people with low vision using zoom with
focus tracking.

Gbp-Pq: Name enable_a11y_on_linux.diff