Fix revert-buffer functionality of Help mode and Info.

Fix revert-buffer functionality of Help mode and Info.

* lisp/help-mode.el (help-mode): Set buffer-local variable
revert-buffer-function to help-mode-revert-buffer.
(help-mode-revert-buffer): New function.

* lisp/info.el (Info-revert-find-node): Check for major-mode Info-mode
before popping to "*info*" (like in other Info functions).
Keep buffer-name in old-buffer-name.  Keep Info-history-forward in
old-history-forward.  Pop to old-buffer-name or "*info*" to
recreate the killed buffer.  Set Info-history-forward from
old-history-forward.
(Info-breadcrumbs-depth): Add :group and :version.