* varobj.c (update_dynamic_varobj_children): Don't use

	* varobj.c (update_dynamic_varobj_children): Don't use
	value_copy.
	* value.h: (preserve_one_value): Declare.
	(value_prepend_to_list, value_remove_from_list): Remove.
	* value.c (preserve_one_value): No longer static.
	(preserve_values): Call preserve_python_values.
	(value_prepend_to_list): Remove.
	(value_remove_from_list): Remove.
	* python/python.h (values_in_python): Don't declare.
	(preserve_python_values): Declare.
	* python/python-value.c (values_in_python): Change type.  Move
	lower.  Now static.
	(struct value_object): Add struct tag.
	<next, prev>: New fields.
	(valpy_dealloc): Update.
	(note_value): New function.
	(valpy_new): Use value_incref, note_value.
	(preserve_python_values): New function.
	(valpy_positive): Don't use value_copy.
	(value_to_value_object): Use value_incref, note_value.
	(convert_value_from_python): Update comment.