(Info-history-forward): New variable.

(Info-history-forward): New variable.
(Info-select-node): Reset Info-history-forward to nil.
(Info-last): Turn into defalias.
(Info-history-back): Rename from Info-last.
Add current node to Info-history-forward.
(Info-history-forward): New fun.
(Info-mode-map): Replace Info-last by Info-history-back.
Bind Info-history-forward to "r".
(Info-mode-menu): Replace Info-last by Info-history-back.
Fix menu item text.  Add menu item for Info-history-forward.
(info-tool-bar-map): Replace Info-last by Info-history-back.
Replace its icon "undo" by "back_arrow".  Add icon "fwd_arrow"
for Info-history-forward.
(Info-mode): Replace Info-last by Info-history-back in docstring.
Add local variable Info-history-forward.
(Info-goto-emacs-command-node): Replace Info-last by Info-history-back.