It simply doesn't seem to work for anything useful, and nobody seems
to care about maintaining it.

This changes the main IOS code (roughly the equivalent of the kernel)
to a class instead of being a set of free functions + tons of static
variables.

The reason for this change is that keeping tons of static variables
like that prevents us from making an IOS instance and reusing IOS
code easily.

Converting the IOS code to a class also allows us to mostly decouple
IOS from the PPC emulation.

The more interesting changes are in Core/IOS/IOS. Everything else is
mostly just boring stuff required by this change...

* Because the devices themselves call back to the main IOS code
  for various things (getting the current version, replying to a
  request, and other syscall-like functions), just like processes in
  IOS call kernel syscalls, we have to pass a reference to the kernel
  to anything that uses IOS syscalls.

* Change DoState to save device names instead of device IDs to simplify
  AddDevice() and get rid of an ugly static count.

* Change ES_Launch's ack to be sent at IOS boot, now that we can do
  this properly.

This is only ever queried and not set outside of the Core.cpp, so this
should just be hidden internally and just have a function exposed that
allows querying it.

Move "Background Input" out of individual controller configurations

Places all of the SI code under the SerialInterface namespace instead of
only the main source file. This keeps all SI code under a common name,
as well as out of the global namespace