org.el (org-adaptive-fill-function): Fix various bugs when filling in message-mode

* org.el (org-adaptive-fill-function): In message-mode, don't
lines in the message header, nor table lines in the body.
Correctly fill lines starting with `org-outline-regexp' in the
body.

lisp/org.el

@@ -20989,53 +20989,56 @@ hierarchy of headlines by UP levels before marking the subtree."
 Return fill prefix, as a string, or nil if current line isn't
 meant to be filled."
   (let (prefix)
-    (when (and (derived-mode-p 'message-mode) (message-in-body-p))
-      (save-excursion
-	(beginning-of-line)
-	(cond ((looking-at message-cite-prefix-regexp)
-	       (setq prefix (match-string-no-properties 0)))
-	      ((looking-at org-outline-regexp)
-	       (setq prefix "")))))
-    (or prefix
-	(org-with-wide-buffer
-	 (let* ((p (line-beginning-position))
-		(element (save-excursion (beginning-of-line) (org-element-at-point)))
-		(type (org-element-type element))
-		(post-affiliated
-		 (save-excursion
-		   (goto-char (org-element-property :begin element))
-		   (while (looking-at org-element--affiliated-re) (forward-line))
-		   (point))))
-	   (unless (< p post-affiliated)
-	     (case type
-	       (comment (looking-at "[ \t]*# ?") (match-string 0))
-	       (footnote-definition "")
-	       ((item plain-list)
-		(make-string (org-list-item-body-column post-affiliated) ? ))
-	       (paragraph
-		;; Fill prefix is usually the same as the current line,
-		;; except if the paragraph is at the beginning of an item.
-		(let ((parent (org-element-property :parent element)))
-		  (cond ((eq (org-element-type parent) 'item)
-			 (make-string (org-list-item-body-column
-				       (org-element-property :begin parent))
-				      ? ))
-			((save-excursion (beginning-of-line) (looking-at "[ \t]+"))
-			 (match-string 0))
-			(t  ""))))
-	       (comment-block
-		;; Only fill contents if P is within block boundaries.
-		(let* ((cbeg (save-excursion (goto-char post-affiliated)
-					     (forward-line)
-					     (point)))
-		       (cend (save-excursion
-			       (goto-char (org-element-property :end element))
-			       (skip-chars-backward " \r\t\n")
-			       (line-beginning-position))))
-		  (when (and (>= p cbeg) (< p cend))
-		    (if (save-excursion (beginning-of-line) (looking-at "[ \t]+"))
-			(match-string 0)
-		      "")))))))))))
+    (catch 'exit
+      (when (derived-mode-p 'message-mode)
+	(save-excursion
+	  (beginning-of-line)
+	  (cond ((or (not (message-in-body-p))
+		     (looking-at orgtbl-line-start-regexp))
+		 (throw 'exit nil))
+		((looking-at message-cite-prefix-regexp)
+		 (throw 'exit (match-string-no-properties 0)))
+		((looking-at org-outline-regexp)
+		 (throw 'exit (make-string (length (match-string 0)) ? ))))))
+      (org-with-wide-buffer
+       (let* ((p (line-beginning-position))
+	      (element (save-excursion (beginning-of-line) (org-element-at-point)))
+	      (type (org-element-type element))
+	      (post-affiliated
+	       (save-excursion
+		 (goto-char (org-element-property :begin element))
+		 (while (looking-at org-element--affiliated-re) (forward-line))
+		 (point))))
+	 (unless (< p post-affiliated)
+	   (case type
+	     (comment (looking-at "[ \t]*# ?") (match-string 0))
+	     (footnote-definition "")
+	     ((item plain-list)
+	      (make-string (org-list-item-body-column post-affiliated) ? ))
+	     (paragraph
+	      ;; Fill prefix is usually the same as the current line,
+	      ;; except if the paragraph is at the beginning of an item.
+	      (let ((parent (org-element-property :parent element)))
+		(cond ((eq (org-element-type parent) 'item)
+		       (make-string (org-list-item-body-column
+				     (org-element-property :begin parent))
+				    ? ))
+		      ((save-excursion (beginning-of-line) (looking-at "[ \t]+"))
+		       (match-string 0))
+		      (t  ""))))
+	     (comment-block
+	      ;; Only fill contents if P is within block boundaries.
+	      (let* ((cbeg (save-excursion (goto-char post-affiliated)
+					   (forward-line)
+					   (point)))
+		     (cend (save-excursion
+			     (goto-char (org-element-property :end element))
+			     (skip-chars-backward " \r\t\n")
+			     (line-beginning-position))))
+		(when (and (>= p cbeg) (< p cend))
+		  (if (save-excursion (beginning-of-line) (looking-at "[ \t]+"))
+		      (match-string 0)
+		    "")))))))))))
 
 (declare-function message-goto-body "message" ())
 (defvar message-cite-prefix-regexp)	; From message.el