2023-05-31  Stephen Berman  <stephen.berman@gmx.net>

	Fix several todo-mode.el item editing bugs (bug#)

	* lisp/calendar/todo-mode.el (todo-insert-item--basic): With
	insertion type 'here', ensure item is inserted on the todo-mode
	line where the command was invoked.
	(todo-edit-item--cat, todo-edit-item--pos): New variables.
	(todo-edit-item--text): Restrict the scope of nil-valued
	buffer-read-only to the functions that change buffer text.  If
	user moved point while editing a single-line todo item or a done
	item comment, or while inserting a done item comment, restore
	point, and for comments, make sure the done items section is
	displayed.  For multiline items, set the new variables so
	todo-edit-quit can use them.
	(todo-edit-quit): Use the values of the new variables to restore
	point in the todo-mode buffer if it had been moved while editing.
	(todo-edit-item--header): Avoid clobbering match data when editing
	a todo item header.