(Info-following-node-name-re): New fun.

(Info-following-node-name-re): New fun.
(Info-following-node-name): Remove.
(Info-insert-dir): Use the new fun.
(Info-extract-pointer): Don't save restriction; use new fun.
(Info-menu-entry-name-re): New const.
(Info-menu-entry-name-re): Use it along with new fun.
(Info-node-spec-re): Use new fun.
(Info-complete-menu-item, Info-fontify-node): Use new const.
(Info-goto-node, Info-follow-reference, Info-menu-update):
Use match-string.
(Info-follow-reference): Use assoc-string.
Use a list of strings for the completion table.
(Info-fontify-node): Use match-string, line-end-position.
Limit the search for `node:' to the first line.