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
Document that giving %NULL for the activate handler is supported since
GLib 2.40. We documented this on GSimpleAction itself (where the
default handler functionality is implemented) but expecting the user to
dig that up is asking a bit much.
Also, add some more explicit documentation about the conditions under
which each field is expected to be filled in.
https://bugzilla.gnome.org/show_bug.cgi?id=732429
Clean up the docs for GApplication and related classes.
I'm no longer writing documentation for the structure type of classes
and interfaces. See https://bugzilla.gnome.org/show_bug.cgi?id=665926
for discussin on the correct way forward on this point.
Also: stop putting gtk-doc comments in installed headers.
This is an interface to represent GSimpleActionGroup-like objects (ie:
those GActionGroups that operate by containing a number of named GAction
instances).
