Add support for :inherit attribute.
Add support for relative face heights.
(custom-face-attributes-get):
Treat `nil' as being a default value for :inherit (as well as `unspecified').
:inverse-video cases. Fix up :box case (probably needs more work).
Change from Didier Verna:
(custom-set-faces): The arguments can now have a custom comment as
fourth argument.
(custom-face-attributes): Add overline, strike-through, box.
(custom-face-attributes): Use `choice' everywhere so that "*"
can be entered.
(custom-face-attributes): Don't use `#''.
(custom-face-attributes): Accept color name.
(custom-facep): Always define as alias for facep.
(custom-face-attributes): Use choice widgets. Remove
:bold and :italic.
(custom-face-attributes): Add :bold and :italic
for compatibility with old code.
(custom-face-attributes): Use new face attributes.
(custom-declare-face): Don't make frame-local faces.
(global): Face relief added.
