Log Message:
Update apel to 10.8.

Changes:
        * EMU-ELS (emu-modules): Add setting for GNU Emacs 23 or later.
        * invisible.el: In GNU Emacs 23, inv-19.el overrides builtin
        function `invisible-p'.  To fix the bug, require `inv-23' when
        running with GNU Emacs 23 or later.
        * poe.el (format-time-string): Fix problem on GNU Emacs 22.2