Merge branch 'debian/stretch-backports' of https://salsa.debian.org/gnome-team/atk into stretch-a11y-layer-backports

This reverts commit 160adab5.

debian/patches/1000-setrole-static

(cherry picked from commit 1aa79ee0)

Update to upstream version '2.30.0'
with Debian dir ec2b6e20e8f107fe9a72c2eebe0d5d29334b2bbe

Revert "atkimplementor: use the G_DEFINE_INTERFACE macro to declare it as interface in the introspection"

This change unintentionally changed the ABI and the introspection ABI.

Fixes:
   https://gitlab.gnome.org/GNOME/atk/issues/1

This reverts commit 30f2712c.

Explicitly refer to character offsets to clear up any confusion with
multi-byte encoding. Fix some typos and tabs.

The coding style needs some tweaking to fit in with the rest of the
code base.

Instead of iterating over them ourselves, Meson 0.46 provides useful
convenience functions.

Using the appropriate Meson functions also removes warnings with newer
versions of Meson.

Version 0.40.1 is ancient history.

Use 0.46.0, as we're going to need some new features.

atkimplementor: use the G_DEFINE_INTERFACE macro to declare it as interface in the introspection

See merge request GNOME/atk!2

gobject-introspection: fix virtual annotations and missing type descriptions

See merge request GNOME/atk!1