Implement ANSI SGR parameters 22-27.

Implement ANSI SGR parameters 22-27.
* lisp/ansi-color.el (ansi-colors): Doc fix.
(ansi-color-context, ansi-color-context-region): Doc fix.
(ansi-color--find-face): New function.
(ansi-color-apply, ansi-color-apply-on-region): Use it.
Rename the local variable `face' to `codes' since it is now a list of
ansi codes.  Doc fix.
(ansi-color-get-face): Remove.
(ansi-color-parse-sequence): New function, derived from
ansi-color-get-face.
(ansi-color-apply-sequence): Use it.  Rewrite, and support ansi
codes 22-27.