These were added in 5e29508b8f4747e92e8de68b75971f26e4a78cd4 and 1f2d43c8709e5fab2f8c3c7de81bdf160b5f6363, but were replaced with CONFIG_CHANGE_BIT_VSYNC and CONFIG_CHANGE_BIT_STEREO_MODE in e4b205c76937d379cd9043939e2cef1651b1a21b.
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.
