[PATCH] Fix texinfo->html for @i, @math, @tie and @dots

[Christopher Baines]

I spotted the following warnings when converting some texinfo to HTML
(for Guix package descriptions).

;;; WARNING (Don't know how to convert *braces* to HTML)
;;; WARNING (Don't know how to convert dots to HTML)
;;; WARNING (Don't know how to convert i to HTML)
;;; WARNING (Don't know how to convert math to HTML)
;;; WARNING (Don't know how to convert tie to HTML)

I'm not sure all the texinfo I was converting is well formed, but in all
but the last 4 cases look possible to fix, and this patch might work. I
wasn't able to get past running the ./configure script, so I haven't
managed to test the changes.

As for *braces*, I'm not quite sure what that relates to.