This formats all copyright comments according to SPDX formatting guidelines.
Additionally, this resolves the remaining GPLv2 only licensed files by relicensing them to GPLv2.0-or-later.
Now that we have most of core free of shadowing, we can enable the
warning as an error to catch anything that may be remaining and also
eliminate this class of logic bug entirely.
Allows reporting more cases where logic errors may exist, such as
implicit fallthrough cases, etc.
We currently ignore unused parameters, since we currently have many
cases where this is intentional (virtual interfaces).
While we're at it, we can also tidy up any existing code that causes
warnings. This also uncovered a few bugs as well.