Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
In particular:
- drop "when it is non-zero" to avoid implying that it can be called if the
queue is not empty.
- "has been created" sounds like something happened in parallel,
but what we really mean is that *this* particular object *was* created in a
certain way.
