New commands for minibuffer history control

New commands for minibuffer history control

* lisp/minibuffer.el (minibuffer-alternate-history)
(minibuffer-kill-from-history): New commands.
(minibuffer-local-map): Bind them.
(minibuffer-hint-mode): Make interactive.
(minibuffer-action-history): New variable.
(minibuffer-set-completion-action): Use it, new command.
(minibuffer-local-completion-map): Bind them.
(minibuffer-apply): Use 'completion-identity', if present.
(read-history-variable-history): New variable.
(read-history-variable): Use it.