org-keys: Re-instate <return> bindings

Reported-by: Bernt Hansen <bernt@norang.ca>
<http://lists.gnu.org/r/emacs-orgmode/2019-01/msg00312.html>

lisp/org-keys.el

@@ -448,11 +448,16 @@ COMMANDS is a list of alternating OLDDEF NEWDEF command names."
 (org-defkey org-mode-map (kbd "S-<tab>") #'org-shifttab)
 (define-key org-mode-map (kbd "<backtab>") #'org-shifttab)
 
-;;;; RET key with modifiers
+;;;; RET/<return> key with modifiers
+(org-defkey org-mode-map (kbd "S-<return>") #'org-table-copy-down)
 (org-defkey org-mode-map (kbd "S-RET") #'org-table-copy-down)
+(org-defkey org-mode-map (kbd "M-S-<return>") #'org-insert-todo-heading)
 (org-defkey org-mode-map (kbd "M-S-RET") #'org-insert-todo-heading)
+(org-defkey org-mode-map (kbd "ESC S-<return>") #'org-insert-todo-heading)
 (org-defkey org-mode-map (kbd "ESC S-RET") #'org-insert-todo-heading)
+(org-defkey org-mode-map (kbd "M-<return>") #'org-meta-return)
 (org-defkey org-mode-map (kbd "M-RET") #'org-meta-return)
+(org-defkey org-mode-map (kbd "ESC <return>") #'org-meta-return)
 (org-defkey org-mode-map (kbd "ESC RET") #'org-meta-return)
 
 ;;;; Cursor keys with modifiers