For thread safety, we shouldn't return any pointers or references that
can be used to mutate the state of the PPCSymbolDB. This should be the
final part of making PPCSymbolDB thread safe unless I've missed
something.
This fixes a problem I was having where using frame advance with the
debugger open would frequently cause panic alerts about invalid addresses
due to the CPU thread changing MSR.DR while the host thread was trying
to access memory.
To aid in tracking down all the places where we weren't properly locking
the CPU, I've created a new type (in Core.h) that you have to pass as a
reference or pointer to functions that require running as the CPU thread.
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.
PowerPC.h at this point is pretty much a general glob of stuff, and it's
unfortunate, since it means pulling in a lot of unrelated header
dependencies and a bunch of other things that don't need to be seen by
things that just want to read memory.
Breaking this out into its own header keeps all the MMU-related stuff
together and also limits the amount of header dependencies being
included (the primary motivation for this being the former reason).
This fix the awkwardness of having the symbols detection, parsing and loading related logs be in OS HLE while they don't have anything to do with that.
