and a machine-independent though inefficient InterlockedExchange().
In Windows, InterlockedExchange() appears to be implemented in header
files via inline assembly. I would prefer using an atomic.h macro for
this, but there doesn't seem to be one that just does a plain old
atomic exchange (as opposed to compare and exchange). Also implement
IoSetCancelRoutine(), which is just a macro that uses InterlockedExchange().
Fill in IoBuildSynchronousFsdRequest(), IoBuildAsynchronousFsdRequest()
and IoBuildDeviceIoControlRequest() so that they do something useful,
and add a bunch of #defines to ntoskrnl_var.h to help make these work.
These may require some tweaks later.
d3e4cd0609