rem: spec_list->head = spec_list->tail = (struct List_element *) xmalloc (sizeof (struct List_element));
add: struct List_element *new = xmalloc (sizeof *new); spec_list->head = spec_list->tail = new;
context: spec_init (struct Spec_list *spec_list){  spec_list->head = spec_list->tail =    (struct List_element *) xmalloc (sizeof (struct List_element));  spec_list->head->next = NULL;}