defctype and inner structs do not seem to play nicely

[Willem Rein Oudshoorn]

With the attached code, the following transcript shows the difference:

CL-USER> (ql:quickload "CFFI")
To load "cffi":
  Load 1 ASDF system:
    cffi
; Loading "cffi"
..
("CFFI")
CL-USER> (use-package "CFFI")
T
CL-USER> (load "/Users/woudshoo/Development/Source/Lisp-Outside-ASDF/cffi-bugs/struct-bug")
STYLE-WARNING: Undefined alien: "get_outer"
T
CL-USER> (setup)
#<FOREIGN-LIBRARY CFFI.O-943 "cffi.o">
CL-USER> (get-outer-works)
"Outer Translated, a = 1, b= <Inner Translated, a = 2, b= 3>"
CL-USER> (get-outer-bug)
"Outer Translated, a = 1, b= <#.(SB-SYS:INT-SAP #X0018E004)>"

The difference in the result is that in '(get-outer-works)' the inner struct is translated and
in the bug version it is not.

As far as I can tell the only relevant difference is in the declaration of the outer structs:

(defcstruct (outer-struct :class outer-struct-type)
  (a :int)
  (b (:struct inner-struct)))

vs

(defctype %bug-struct (:struct inner-struct))

(defcstruct (outer-struct-bug :class outer-struct-type-bug)
  (a :int)
  (b %bug-struct))