Detailed changes:
- proton,staging: never quite liked these IUSE, this virtual is
not intended for users to pick wine through USE (they can just
e.g. add wine-staging to world file), and seems no packages
depend on specific wine variants through this and it would be
annoying for users to set these USE if they did
- wow64: allowing as an option should remove the need for users
to unset abi_x86_32 when they use it
- keyword for ~arm64, it's an option now and no need for keywordreq
for a virtual
- drop REQUIRED_USE, arm64 is also an option over abi_x86_* and
there's no real reason to enforce at least one being set here
- while here, swap `abi_x86_64=` by `abi_x86_64?`, the former
tend to give confusing portage messages and is not needed here
Signed-off-by: Ionen Wolkens <ionen@gentoo.org>
4b683463aa