arrange_return_to_lisp_function(), but this looked hard to do in
general without suffering from memory leaks.
-378: floating-point exceptions not signalled on x86-64
- Floating point traps are currently not enabled on the x86-64 port.
- This is true for at least overflow detection (as tested in
- float.pure.lisp) and divide-by-zero.
-
379: TRACE :ENCAPSULATE NIL broken on ppc/darwin
See commented-out test-case in debug.impure.lisp.