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.
This allows for better compiler errors, where the compiler will state a
copy or move couldn't occur due to the relevant function being deleted.
Previously a compiler would warn about the relevant function not being
accessible (which, while true, isn't as informative as it could be).
