bug#2820: 23.0.91; ruby-mode binds keys it probably shouldn't

[Dmitry Gutov]

Revision 109870 has cleaned up most of the keybindings, including 
ruby-beginning-of-defun.

I left out these:
1) ruby-forward/backward-sexp - because these functions are sufficiently 
different from the default (forward-sexp).
Just setting forward-sexp-function value would break `up-list' and 
`backward-up-list', for example.
2) ruby-indent-exp - because it's more useful than `prog-indent-sexp', 
and the latter uses `forward-sexp'.

Can we consider this bug fixed?

--Dmitry