The platform independent Processor.h file includes the shared processor
code and includes the specific platform header file.
All references to the Arch/x86/Processor.h file have been replaced with
a reference to Arch/Processor.h.
This class acts like a combined ref-count as well as a spin-lock
(only when adding the first or removing the last reference), allowing
to run a specific action atomically when adding the first or dropping
the last reference.