The logging was broken in 958cbf38a4 (DSPTool doesn't use dolphin's logging system, so it just produced nothing; the same thing affected comparing before 693a29f8ce).
AssemblerError::LabelAlreadyExists (previously ERR_LABEL_EXISTS) simply was never used.
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.
We can std::move the std::string parameter in Label's constructor,
allowing the constructor to be moved into in calling code.
We can cascade this outwards in the interface as well.
Given this is a private struct and it's used in a container that
supports incomplete types, we can forward-declare it and move it into
the cpp file. While we're at it, we can change the name to Label to
follow our formatting guidelines.
We also move the destructor definition into the cpp file, as that will
allow us to make the entire label_t type hidden from external view in a
following change.
