Add historical option to completions-sort

Add historical option to completions-sort

Support sorting candidates in *Completions* by the order they show up
in the minibuffer history.

Also add minibuffer-sort-alphabetically and
minibuffer-sort-by-history, which are usable for both completions-sort
and display-sort-function.

* lisp/minibuffer.el (completions-sort): Document 'historical option.
(minibuffer-completion-help): Support 'historical option.
(minibuffer-sort-alphabetically)
(minibuffer-completion-base, minibuffer-sort-by-history): Add.
* etc/NEWS: Announce it.