bug#3370: 23.0.94; `comment-region' indents comment chars inappropriately

[Chong Yidong]

> In buffer *scratch*, type this: SPC SPC ` a b c d e f ' RET
>
> Select the line, including the newline at its end: `M-< C-SPC C-n'.
> M-x comment-region
> 
> In Emacs 23, this is the result:
> 
>   ;; `abcdef'
> 
> In all previous versions of Emacs, the comment chars are inserted at
> the start of the line - they are not indented two spaces

Wrong.  The behavior is identical in Emacs 22.