bug#7240: 24.0.50; [PATCH] backward-sentence sometimes overshoots (and breaks doctor)

[Wolfgang Jenkner <wjenkner@inode.at>]

RMS's last change to backward-sentence leaves that command broken.

Create a buffer like this

---------- Buffer: foo ---------

  This sentence follows some spaces.
---------- Buffer: foo ---------

Set point somewhere after the first character of the second line and
type M-a (which runs backward-sentence).

Point is now at the beginning of the second line, but it should be at
the `T' (cf. (emacs)Top > Text > Sentences).

Obviously, I suggest reverting that change and applying my patch
instead.