Improve the cursor-face feature.

Improve the cursor-face feature.

Use a minor mode to reduce potential performance issues.

* lisp/simple.el (cursor-face-highlight-mode) : New minor mode
(completion-setup-function) : Use the new minor mode
cursor-face-highlight-mode in completions.
(redisplay--unhighlight-overlay-function) : Add -- to the name
(redisplay--highlight-overlay-function) : Make the face parameter
optional and add -- in the name.