(desktop-internal-v2s): Allow saving of markers and subrs.

(desktop-internal-v2s): Allow saving of markers and subrs.
(desktop-delay-hook): New variable.
(desktop-read): Run desktop-delay-hook.
(desktop-globals-to-save): Save register-alist.
Always make desktop-locals-to-save local.
(desktop-value-to-string): Make sure floating point numbers are
output with maximum accuracy.
(desktop-bug-report): New function.

(desktop-internal-v2s): New function.
(desktop-value-to-string): Use above function.

(desktop-buffers-not-to-save): Add regexp for "nn" temporary files.
(desktop-save, <top-level>): Remove support for Emacs 18, because
it's not worth the effort and didn't work anymore, anyway.
(desktop-save): Needn't bind `print-escape-newlines' anymore.