Make it a bit more obvious that the changed properties are provided as
an a{sv}.

Signed-off-by: Philip Withnall <withnall@endlessm.com>
Reviewed-by: nobody

priv->map_object_path_to_object_proxy must be protected to avoid
concurrent access by multiple threads. Move the hash table insertion
into the critical section.

https://bugzilla.gnome.org/show_bug.cgi?id=788368

https://bugzilla.gnome.org/show_bug.cgi?id=756009

Sub-directories inside gio/ already processed in a previous commit:
- fam/
- gdbus-2.0/ (which contains only codegen/)
- gvdb/
- inotify/
- tests/
- win32/
- xdgmime/

Other sub-directories inside gio/:
- completion/: no license headers
- kqueue/: not LGPL, BSD-style license

https://bugzilla.gnome.org/show_bug.cgi?id=776504

It's unnecessary, and only adds visual noise; we have been fairly
inconsistent in the past, but the semi-colon-less version clearly
dominates in the code base.

https://bugzilla.gnome.org/show_bug.cgi?id=669355

If we have an input parameter (or return value) we need to use (nullable).
However, if it is an (inout) or (out) parameter, (optional) is sufficient.

It looks like (nullable) could be used for everything according to the
Annotation documentation, but (optional) is more specific.

This avoids pointless copying of static strings.

And remove remaining unnecessary gsimpleasyncresult.h includes

When establishing a D-Bus connection failed, g_dbus_object_manager_client_finalize()
calls g_object_ref(manager->priv->connection) when that pointer is NULL,
which is considered and logged as error by glib.

https://bugzilla.gnome.org/show_bug.cgi?id=732984

https://bugzilla.gnome.org/show_bug.cgi?id=730493