bug#11095: [PATCH] Re: bug#11095: 24.0.94; hi-lock-face-buffer/unhighlight-regexp': Augment?

[Stefan Monnier]

> This patch makes sure that faces used for highlighting are always
> distinct and recycles them only when it is inevitable.

Installed with 2 changes:
- replace "delete" with "remove" because it was applied to a list which
  is reachable from other places (basically, from other buffer's
  hi-lock--unused-faces).
- introduced a helper hi-lock-keyword->face to get rid of those cadadadr
  (some of which needed `cl' even it was not `require'd).


        Stefan