Fix various 32/64-bit portability issues in ssp, the single-step profiler, and
also build it for 64-bit.
This didn't turn out to actually be very useful for what I wanted to use it for,
so it's only been lightly tested.
It appears that on x86_64, single-step exceptions occur for much more of the
code in system DLLs, unlike x86, so ssp may take much, much longer to profile
some programs. There is existing code to use breakpoints to mitigate this, but
that is currently disabled.
Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>
658caa7640