(custom-new-theme-mode): New function.

(custom-new-theme-mode): New function.
(custom-theme-name, custom-theme-variables, custom-theme-faces)
(custom-theme-description): Add compiler defvars.
(customize-create-theme): Add doc to the "*New Custom Theme*"
buffer.  Use `custom-new-theme-mode'.
(custom-theme-write): Put the created buffer in emacs-lisp-mode
and save it to the `custom-theme-directory'.  Make this the
default directory of the buffer.