bug#1443: 23.0.60; key bindings in help-mode

[Leo]

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the emacs-pretest-bug@gnu.org mailing list.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

It looks like help-mode is always read-only, thus the key bindings to
help-go-back and help-go-forward can be simplified to 'b' and 'f', or
'l' and 'r' (to be consistent with info mode), instead of 'C-c C-b' and
'C-c C-f'.