[CM] fun with CM + Linux

[Bill Schottstaedt]

It might be significant that the segfault happens at:

                       #.(SYSTEM:INT-SAP #x3FFFEAE0))

This is in CMUCL, and is called only in ffi.lisp when I'm trying to
pass an array from Lisp to C (or vice versa?). But that doesn't happen
at all in start-snd!  In the best of all worlds, you'd be able to run
cmucl under gdb, fall into gdb upon the segfault, then look at the
stack and locals to see what has gone awry (there's an example in
clm.html), but that trick rarely works in cmucl -- you'll just see a
bunch of question marks or completely bogus entries.