I found ob-lisp.el use SLIME by default to evaluate lisp code. I want to
use SLY to evaluate lisp code. How to change it? I found the file ob-lisp.el
is short. I tried to change slime to sly.

But it is not customizable. I hope to define a defcustom for it. So that
user can customize it. But I don't know how to apply this into code. For
example, I define a custom like this:

```

(defcustom org-babel-lisp-default-implement "slime")
((defcustom org-babel-lisp-implements
   '("slime" "sly")
   "A list of Lisp implements."
   :group 'org-babel
   :version "24.1"
   ;; FIXME: reference code example.
   :type listp))
```


Then in file ob-lisp.el. Has some places use slime. I want to make
them adapt to upper defcustom value. like concate string from value or
something else.

```
(declare-function slime-eval "ext:slime" (sexp &optional package))
(defun org-babel-execute:lisp (body params)
  "Execute a block of Common Lisp code with Babel."
  (require 'slime)
  (org-babel-reassemble-table
   (let ((result
          (funcall (if (member "output" (cdr (assoc :result-params params)))
                       #'car #'cadr)
                   (with-temp-buffer
                     (insert (org-babel-expand-body:lisp body params))
                     (slime-eval `(swank:eval-and-grab-output....
```



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