* cus-theme.el: Rewrite the Custom New Theme Mode interface.

* cus-theme.el: Rewrite the Custom New Theme Mode interface.
	(custom-new-theme-mode-map, custom-theme-insert-variable-marker)
	(custom-theme-insert-face-marker, custom-theme-variable-menu)
	(custom-theme-face-menu): New variables.
	(custom-theme-add-variable, custom-theme-variable-action)
	(custom-variable-reset-theme, custom-theme-delete-variable)
	(custom-face-reset-theme, custom-theme-face-action)
	(custom-theme-delete-face, custom-theme-merge-theme)
	(custom-theme-add-face, custom-theme-visit-theme): New functions.