s390: implement sotruss support

See commit 41b17926 for testcase.

Note: while this works on s390x, the s390 code hangs when using -e.
But it hangs regardless of this code (the hang seems to occur before
the exit func is even called).  I didn't look too closely at it as
it seems to be an issue external to this file, so this code shouldn't
make the situation any worse.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>