gobject-introspection: update to 1.62.0

pkgsrc-specific changes: note Python 2.7 is no longer supported
(upstream dropped it several releases ago), and add a test target.

Change log:

1.62.0 - 2019-09-09
-------------------

* No changes since 1.61.2

1.61.2 - 2019-08-17
-------------------

* dumper: Use the distutils linker :mr:`170` (:user:`David Demelier <markand>`)
* structinfo: Fix offset in find_method() :mr:`171` (:user:`Florian M端llner <fmuellner>`)
* tests: Don't include "config.h" in installed files :mr:`172` (:user:`Philip Chimento <ptomato>`)
* meson: Make meson.override_find_program working on more complex use cases :mr:`173` (:user:`Thibault Saunier <thiblahute>`)

1.61.1 - 2019-08-07
-------------------

* Drop autotools build system :mr:`143`
* meson: require 0.49.2
* Update glib annotations (:user:`Rico Tzschichholz <ricotz>`)
* Add documentation to the RelaxNG schema :mr:`139` (:user:`David Bellot <yimyom>`)
* Unused variable fixes :mr:`147` (:user:`Philip Chimento <ptomato>`)
* cachestore: handle cache getting deleted while loading it :mr:`148`
* Visual Studio builds: Use msvc_recommended_pragmas.h from GLib :mr:`150` (:user:`Chun-wei Fan <fanc999>`)
* Add Vulkan gir :mr:`155` (:user:`Matthew Waters <ystreet00>`)
* Make g_irepository_get_object_gtype_interfaces actually work :mr:`157` (:user:`Philip Chimento <ptomato>`)
* gimarshallingtests: Add a marshalling test case for GPtrArrays and GArrays of structures :mr:`160` (:user:`St辿phane Seng <stephaneseng>`)
* scanner: parse and expose function macros :mr:`159` (:user:`Mathieu Duponchelle <mathieudu>`)
* meson: use pkg-config directly for libffi cflags and libs :mr:`162` (:user:`Aaron Boxer <boxerab>`)
* meson: Fix wrong dependency type check for gio-unix :issue:`166` (:user:`Brook Milligan <brook-milligan>`)
* regress: Add regression test for signal with GError param :mr:`169` (:user:`Philip Chimento <ptomato>`)


(gutteridge)