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 glib/*.[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
We need stronger alignment guarantees for the memory allocations done
through g_rc_box_alloc_full(): while the passed block size may be
aligned, we're not aligning the private data size; this means the
overall allocation may become unaligned, and this could raise issues
when we use the private data size as an offset to access the reference
count.
Fixes: #1581
GArcBox is the atomic reference counting version of GRcBox. Unlike
GRcBox, the reference acquisition and release on GArcBox are guaranteed
to be atomic, and thus they can be performed from different threads.
This is similar to Rust's Arc<Box<T>> combination of traits.
