bug#35381: 26.2; nxml-mode doesn't fontify attributes in single quotes

[Noam Postavsky <npostavs@gmail.com>]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

>> +(defvar sgml-specials '(?\" ?\')
>>    "List of characters that have a special meaning for SGML mode.
>>  This list is used when first loading the `sgml-mode' library.
>>  The supported characters and potential disadvantages are:
>
> I think this "disadvantages" part of the docstring is out of date.
> Can you update it while you're at it?
>
> Also, we probably want to mark this var as obsolete.

I'm not sure about this, is the disadvantage of the ?- also out of date?
There's some FIXME on the "--" rule of sgml-syntax-propertize-rules,
 
-;; As long as Emacs's syntax can't be complemented with predicates to context
-;; sensitively confirm the syntax of characters, we have to live with this
-;; kludgy kind of tradeoff.
 (defvar sgml-specials '(?\" ?\')
   "List of characters that have a special meaning for SGML mode.
 This list is used when first loading the `sgml-mode' library.
-The supported characters and potential disadvantages are:
-
-  ?\\\"	Makes \" in text start a string.
-  ?\\='	Makes \\=' in text start a string.
-  ?-	Makes -- in text start a comment.
-
-When only one of ?\\\" or ?\\=' are included, \"\\='\" or \\='\"\\=', as can be found in
-DTDs, start a string.  To partially avoid this problem this also makes these
-self insert as named entities depending on `sgml-quick-keys'.
+The supported characters are ?\\\", ?\\=', and ?-.
 
 Including ?- has the problem of affecting dashes that have nothing to do
 with comments, so we normally turn it off.")