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.
The STL has everything we need nowadays.
I have tried to not alter any behavior or semantics with this
change wherever possible. In particular, WriteLow and WriteHigh
in CommandProcessor retain the ability to accidentally undo
another thread's write to the upper half or lower half
respectively. If that should be fixed, it should be done in a
separate commit for clarity. One thing did change: The places
where we were using += on a volatile variable (not an atomic
operation) are now using fetch_add (actually an atomic operation).
Tested with single core and dual core on x86-64 and AArch64.
Replaces them with forward declarations of used types, or removes them entirely if they aren't used at all. This also replaces certain Common headers with less inclusive ones (in terms of definitions they pull in).
Design doc:
https://docs.google.com/document/d/11qcGCWLne1wYvmtFaSrOKZt_vHxXrcWcZsdWJ-MJnyo/edit
The code is currently not used. Migration plan:
1. Implement MMIO access via MMIO::Mapping in parallel to the current
method.
2. Implement all existing MMIO handlers via the new interface.
3. Remove the old hwRead/hwReadWii/hwReadIOBridge code.
4. Implement JIT optimizations for MMIO accesses.
