bug#11189: 24.0.95; texinfmt deletes " and \ at bol

[Katsumi Yamaoka <yamaoka@jpl.org>]

Hi,

Please try `M-x texinfo-format-buffer' in a buffer filled with
this text:

--8<---------------cut here---------------start------------->8---
@setfilename /tmp/test

111 111 111 111 111 111 111 111 111 111 111 111 111 111 111 111 111 @dfn{FOO}

222 222 222 222 222 222 222 222 222 222 222 222 222 222 222 222 222 ``BAR''

333 333 333 333 333 333 333 333 333 333 333 333 333 333 333 333 333 \BAZ/
--8<---------------cut here---------------end--------------->8---

@dfn{FOO} and ``BAR'' should be formatted into "FOO" and "BAR"
respectively, but you will see the leftmost " and \ disappear.
This happens with not only Emacs 24 but also at least Emacs 23.

`back-to-indentation' does it in this way

  texinfo-format-refill
    -> fill-paragraph
      -> fill-indent-to-left-margin
        -> indent-line-to
          -> back-to-indentation

because `texinfo-format-syntax-table' sets the character syntax
of " and \ to " ".  Though I'm not sure whether that is the root
cause, modifying those syntax to "w" seems to work around it.

Note that texinfmt.el is still indispensable for formatting non-
English texinfo files.

Regards,