Don't just use ControlPcIsUnwound for picking which RUNTIME_FUNCTION
to use, but also use it for adjusting the pc value that is passed
to RtlVirtualUnwind.

This fixes one testcase (that I had missed to build and run before),
where the pc points at the start of an epilogue (which would mean
that no handler is returned from RtlVirtualUnwind). By taking
ControlPcIsUnwound and adjusting the pc pointer, the unwind handler
is returned and executed.
Signed-off-by: Martin Storsjö <martin@martin.st>