(help-highlight-face): Use underline.

(help-highlight-face): Use underline.
(help-mode-maybe): Ensure read-only.
(help-xref-button): Obey help-highlight-p.
(help-follow): Remove check for args being a list.
(help-mode): Doc fix.
(help-highlight-p): Put in help group.

(help-make-xrefs): Insert button label in scope of
inhibit-read-only binding.
(help-mode-map, help-make-xrefs): Define TAB, RET correctly.

Make hyperlinks for cross-reference info intuited from *Help* buffer.
(help-font-lock-keywords): Removed.
(help-mode-map): Define keys for navigating hyperlinks.
(help-xref-stack, help-xref-stack-item): New permanent-local variables.
(help-mode): Set font-lock-defaults to nil.
(help-mode-maybe): Invoke help-make-xrefs in Help mode.
(help-setup-xref): New function.
(describe-key, describe-mode, describe-function,
describe-variable): Call it.
(view-lossage, describe-bindings): Nullify help-xref-stack,
help-xref-stack-item.
(help-highlight-p): New option.
(help-highlight-face): New variable.
(help-back-label, help-xref-symbol-regexp, help-xref-info-regexp):
New variables.
(help-setup-xref, help-make-xrefs, help-xref-button,
help-xref-interned, help-xref-mode, help-follow-mouse,
help-xref-go-back, help-go-back, help-follow, help-next-ref): New functions.