org-mobile.el (org-mobile-edit): Insert new headings at the end of the parent subtree

* org-mobile.el (org-mobile-edit): Insert new headings at the
end of the parent subtree.  Use `org-at-heading-p' instead of
the obsolete `org-on-heading-p'.

Thanks to James Harkins for reporting this.

lisp/org-mobile.el

@@ -1066,13 +1066,13 @@ be returned that indicates what went wrong."
 	 (t (error "Heading changed in MobileOrg and on the computer")))))
 
      ((eq what 'addheading)
-      (if (org-on-heading-p) ; if false we are in top-level of file
+      (if (org-at-heading-p) ; if false we are in top-level of file
 	  (progn
 	    ;; Workaround a `org-insert-heading-respect-content' bug
 	    ;; which prevents correct insertion when point is invisible
 	    (org-show-subtree)
 	    (end-of-line 1)
-	    (org-insert-heading-respect-content '(4) t)
+	    (org-insert-heading-respect-content '(16) t)
 	    (org-demote))
 	(beginning-of-line)
 	(insert "* "))
@@ -1081,7 +1081,7 @@ be returned that indicates what went wrong."
      ((eq what 'refile)
       (org-copy-subtree)
       (org-with-point-at (org-mobile-locate-entry new)
-	(if (org-on-heading-p) ; if false we are in top-level of file
+	(if (org-at-heading-p) ; if false we are in top-level of file
 	    (progn
 	      (setq level (org-get-valid-level (funcall outline-level) 1))
 	      (org-end-of-subtree t t)