This apparently didn't compile on macOS six years ago before c++20, but
it should be fine by now.
While I'm at it, make the constants upper case per convention.
This lets the TAS input code use a higher-level interface for
overriding inputs instead of having to fiddle with raw bits.
WiiTASInputWindow in particular was messy with how much
controller code it had to re-implement.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
