Fix `org-insert-heading-respect-content'

* org-mobile.el (org-mobile-edit): DTRT when inserting a heading
in an invisible region.

* org.el (org-insert-heading-respect-content): New
`invisible-ok' parameter.  Add docstring.
(org-insert-todo-heading-respect-content): Add docstring.

Thanks to James Harkins for the extra detailed reports and
the proposed solutions, both for org.el and org-mobile.el.

lisp/org-mobile.el

@@ -1064,7 +1064,7 @@ be returned that indicates what went wrong."
       (if (org-on-heading-p) ; if false we are in top-level of file
 	  (progn
 	    (end-of-line 1)
-	    (org-insert-heading-respect-content)
+	    (org-insert-heading-respect-content t)
 	    (org-demote))
 	(beginning-of-line)
 	(insert "* "))

lisp/org.el

@@ -7231,12 +7231,14 @@ This is a list with the following elements:
   (org-move-subtree-down)
   (end-of-line 1))
 
-(defun org-insert-heading-respect-content ()
-  (interactive)
+(defun org-insert-heading-respect-content (invisible-ok)
+  "Insert heading with `org-insert-heading-respect-content' set to t."
+  (interactive "P")
   (let ((org-insert-heading-respect-content t))
-    (org-insert-heading t)))
+    (org-insert-heading t invisible-ok)))
 
 (defun org-insert-todo-heading-respect-content (&optional force-state)
+  "Insert TODO heading with `org-insert-heading-respect-content' set to t."
   (interactive "P")
   (let ((org-insert-heading-respect-content t))
     (org-insert-todo-heading force-state t)))