ob-J.el: Add ability to customize sit duration

* lisp/ob-J.el (org-babel-execute:J, org-babel-J-eval-string): Add
customizability.

(org-babel-execute:J): Lookup optional parameter `:sit' to allow one
to wait for a specified amount of time before grabbing the output of
the J subprocess.  Pass this specified value or the previous default
of .1 to `org-babel-J-eval-string'.
(org-babel-eval-string): Pass new argument `sit-time' to `sit-for'
before grabbing output.

The problem is that we read the contents of the output after 0.1
seconds, which, for expensive computations, results in the mangling of
output.  Output from expensive computations gets propagated down to
subsequent code-blocks' outputs, producing a horrible mess.

TINYCHANGE

lisp/ob-J.el

@@ -76,6 +76,8 @@ This function is called by `org-babel-execute-src-block'."
   (message "executing J source code block")
   (let* ((processed-params (org-babel-process-params params))
 	 (sessionp (cdr (assq :session params)))
+	 (sit-time (let ((sit (assq :sit params)))
+		     (if sit (cdr sit) .1)))
          (full-body (org-babel-expand-body:J
                      body params processed-params))
 	 (tmp-script-file (org-babel-temp-file "J-src")))
@@ -86,9 +88,9 @@ This function is called by `org-babel-execute-src-block'."
 	   (with-temp-file tmp-script-file
 	     (insert full-body))
 	   (org-babel-eval (format "%s < %s" org-babel-J-command tmp-script-file) ""))
-       (org-babel-J-eval-string full-body)))))
+       (org-babel-J-eval-string full-body sit-time)))))
 
-(defun org-babel-J-eval-string (str)
+(defun org-babel-J-eval-string (str sit-time)
   "Sends STR to the `j-console-cmd' session and executes it."
   (let ((session (j-console-ensure-session)))
     (with-current-buffer (process-buffer session)
@@ -96,7 +98,7 @@ This function is called by `org-babel-execute-src-block'."
       (insert (format "\n%s\n" str))
       (let ((beg (point)))
 	(comint-send-input)
-	(sit-for .1)
+	(sit-for sit-time)
 	(buffer-substring-no-properties
 	 beg (point-max))))))