info faces for strings and quotations

[Drew Adams]

I find Info to be a lot more readable with strings ("blah blah toto titi")
and quoted names (`my-foobar-function') highlighted in different faces from
the rest of the text.

What about adding something simple like this to the end of
Info-fontify-node - just before (set-buffer-modified-p nil):

  (goto-char (point-min))
  (while (re-search-forward "`\\([^']+\\)'" nil t)
    (put-text-property (match-beginning 1) (match-end 1)
                       'face info-quoted-name-face))
  (goto-char (point-min))
  (while (re-search-forward "\"\\([^\"]+\\)\"" nil t)
    (put-text-property (match-beginning 1) (match-end 1)
                       'face info-string-face))

Granted, there are a few Info nodes that get thrown off by this simple
matching because of unbalanced double or single quotes. This happens when a
node discusses characters like \", \`, and \' or uses this, where the two
are nested: `""'.

Probably most of these problems could be eliminated by smartening up the
regexps. Most of the "rogue" occurrences of these characters are preceded by
backslashes: \".

Even with these simple regexps, however, 99% of the pages look better, and
the text is much more readable, IMO. In particular, it is very helpful that
quoted names stand out; the double-quoted strings are less important.

To see this at its _worst_, these are the nodes of the Emacs manual that
throw off the regexps to some extent:

 - Glossary
 - Key (Character) Index
 - Minor Modes
 - Init Syntax
 - Printing and MS-DOS
 - Cursor Position Information (at the bottom)
 - TeX Editing Commands
 - Options Controlling Comments
 - Etags Regexps
 - Acknowledgements