Fixes related to face underlining

Fixes related to face underlining

* lisp/faces.el (face-underline-p): Doc fix.  Handle :underline being
things other than `t' (a string, a list).
(face-inverse-video-p): Doc fix.
(set-face-underline): Rename it back from set-face-underline-p.
Doc fix.  Allow interactive input of values other than t.
(read-face-attribute): Apply formatting to :underline,
since like :box and :stipple it can take list values.

* doc/lispref/display.texi (Face Attributes): Fix :underline COLOR description.
(Attribute Functions): Update for set-face-underline rename.
Tweak descriptions of face-underline-p, face-inverse-video-p.

* etc/NEWS: Related edit.