Co-authored-by: Victor Perevertkin <victor.perevertkin@reactos.org>
Introduce the initial changes needed to get other processors up and into kernel mode.
This only supports x86 as of now but is the first real step towards using other system processors.
- Rename UP -> PIC. The "up" folder in fact contains the code for
managing the Intel 8259 PIC chip
- Move amd64/processor.c -> apic/processor.c. The code is not tied to
amd64
- Remove platform from "halinit*" files. They already reside in the
corresponding folder
