Revert "org-babel-comint-with-output is now fully self-contained and side-effect free"

  This seems to be causing problems...

This reverts commit 0573fc4d9cd0377a93facf2e0254e67d9f6cfb71.

lisp/org-babel-comint.el

@@ -51,15 +51,15 @@ body inside the protection of `save-window-excursion' and
        (set-buffer buffer)
        ,@body)))
 
+(defun org-babel-comint-append-output-filter (text)
+  (setq string-buffer (concat string-buffer text)))
+
 (defmacro org-babel-comint-with-output (&rest body)
-  (let ((my-filter (gensym "org-babel-comint-filter")))
-    `(let ((string-buffer ""))
-       (flet ((,my-filter (text)
-                          (setq string-buffer (concat string-buffer text))))
-         (add-hook 'comint-output-filter-functions ',my-filter)
-         (condition-case nil (progn ,@body) (t))
-         (remove-hook 'comint-output-filter-functions ',my-filter))
-       string-buffer)))
+  `(let ((string-buffer ""))
+     (add-hook 'comint-output-filter-functions 'org-babel-comint-append-output-filter)
+     (condition-case nil (progn ,@body) (t))
+     (remove-hook 'comint-output-filter-functions 'org-babel-comint-append-output-filter)
+     string-buffer))
 
 (defun org-babel-comint-command-to-output (buffer cmd)
   "Pass CMD to BUFFER using `org-babel-comint-input-command', and