Add SPDX license (but not copyright) headers to all files which follow a
certain pattern in their existing non-machine-readable header comment.
This commit was entirely generated using the command:
```
git ls-files gio/*.[ch] | xargs perl -0777 -pi -e 's/\n \*\n \* This library is free software; you can redistribute it and\/or\n \* modify it under the terms of the GNU Lesser General Public/\n \*\n \* SPDX-License-Identifier: LGPL-2.1-or-later\n \*\n \* This library is free software; you can redistribute it and\/or\n \* modify it under the terms of the GNU Lesser General Public/igs'
```
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #1415
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.
We don't use # or other forms of links in the section headings.
We also capitalize them and don't put a final period.
This commit corrects several headings to follow these rules.
This interfaceifies the extra functions that were on GDBusActionGroup
for dealing with platform data.
The two main benefits of doing this:
- no longer have to do a silly song and dance in GApplication to avoid
calling GDBusActionGroup API from non-dbus-aware code
- the interface can be reused by the action group exporter to avoid
ugly and unbindable hook callbacks
https://bugzilla.gnome.org/show_bug.cgi?id=665737
