bug#16439: [feature request] Highlighting of strings within Info buffers

[Juri Linkov <juri@jurta.org>]

> I agree, and didn't say anything to the contrary.  I told about the
> slant typeface as an evidence that what came out of @dfn should be
> emphasized in some way.

I don't understand the difference between using @dfn and double quotes,
e.g. why in the source of the chapter "The Organization of the Screen":

    The main area of the frame, below the tool bar (if one exists) and
  above the echo area, is called @dfn{the window}.  Henceforth in this
  manual, we will use the word ``window'' in this sense.

the different styles are used for @dfn{the window} and ``window''?

But if both were written in the Info output using DOUBLE QUOTATION MARK
as “window”, then in the Info browser we could emphasize such terms
using the slant typeface and put invisible properties on quote characters.

Then if code blocks such as e.g. in @code{("/foo" "/bar" @dots{})}
were written using simple quotation marks e.g. ("/foo" "/bar" …)
then it would make sense to highlight quoted strings in Info
in code samples using `font-lock-string-face'.

This problem doesn't exist in HTML output that keeps all different source
styles unambiguous, e.g.:

     <p>The main area of the frame, below the tool bar (if one exists) and
  above the echo area, is called <dfn>the window</dfn>.  Henceforth in this
  manual, we will use the word &ldquo;window&rdquo; in this sense.

  <code>(&quot;/foo&quot; &quot;/bar&quot; &hellip;)</code>

where only strings in &quot; inside <code> makes sense
to highlight using `font-lock-string-face'.