* custom.el: Move Custom Themes commentary to start of theme code.

* custom.el: Move Custom Themes commentary to start of theme code.
	(custom-known-themes): Rename `standard' theme to `changed'.
	(custom-push-theme): Caller no longer specifies what theme to use
	when doing `reset'---the setting is simply removed from the theme.
	Delete MODE from `theme-value' and `theme-settings' properties.
	(custom-declare-theme): Ignore &rest args since we don't use them.

	(custom-loaded-themes): Delete variable.
	(custom-theme-load-themes, custom-theme-loaded-p)
	(custom-theme-value): Delete functions.

	(custom-declare-theme): Signal error on invalid theme names.
	(provide-theme): custom-loaded-themes was deleted.
	(load-theme): Load the file unconditionally.
	(enable-theme): Call `load-theme' if theme is undefined.
	(custom-enabled-themes): Only update value for successful loads.
	(disable-theme): Complete from enabled themes when interactive.
	(custom-variable-theme-value): Calculate theme value directly.

	(custom-theme-reset-variables, custom-reset-variables): Mark as
	XEmacs compatibility functions.  We don't actually use these.

	* cus-edit.el (custom-variable-state-set): Use
	custom-variable-theme-value instead of custom-theme-value.
	(custom-face-state-set): Rename `standard' theme to `changed'.
	(custom-save-variables, custom-save-faces): Delete unneeded
	references to custom-reset-variables.
	(custom-save-resets): Delete function.
	(custom-save-variables, custom-save-faces): MODE argument deleted.
	(custom-save-variables, custom-save-faces): Ignore theme values.

	* cus-face.el (custom-theme-reset-faces): Mark as XEmacs
	compatibility function.