Update inspect.lisp for more SBCL internal changes

[lispnik]

This fixes #3 I pulled the code from SBCL's included sb-aclrepl which still shares a close lineage.

$ sbcl
This is SBCL 2.1.6, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses.  See the CREDITS and COPYING files in the
distribution for more information.
* (ql:quickload "prepl")
To load "prepl":
  Load 1 ASDF system:
    prepl
; Loading "prepl"

("prepl")
* (prepl:repl)
Portable REPL on SBCL, main thread.  Type :help for help.
CL-USER> (defstruct foo x y)
FOO
CL-USER> :in (make-foo :x 123 :y 456)

#<STRUCTURE-CLASS COMMON-LISP-USER::FOO> at #x0000001001B41EA0
   0 X --------------> fixnum 123
   1 Y --------------> fixnum 456
[1i] CL-USER> 

[luismbo]

Do you think it would be worthwhile to support older SBCL versions with conditionals?

[lispnik]

@luismbo I don't know. I'll look into if it it's a thing, though. What are your thoughts?

[luismbo]

@lispnik SLIME's SBCL backend typically does things like this: https://github.com/slime/slime/blob/68f5623f13c9a0d3d47ce70cf56928e00483d9d6/swank/sbcl.lisp#L459 If you have the time and inclination, it might be nice to do something similar here. If not, I'm happy to merge this pull request as is.

[xach]

Any update on this? It would be nice to support old and new together if possible.

[lispnik]

Thanks for the reminder, I’ll try get it to work for older SBCL releases.