Fix leafo#531 :

In CSS, identifiers (including element names, classes, and IDs in selectors) can contain only the characters [a-zA-Z0-9] and ISO 10646 characters U+00A0 and higher, plus the hyphen (-) and the underscore (_); they cannot start with a digit, two hyphens, or a hyphen followed by a digit. Identifiers can also contain escaped characters and any ISO 10646 character as a numeric code (see next item).

Author: Cerdic

src/Parser.php

@@ -2477,7 +2477,7 @@ protected function keyword(&$word, $eatWhitespace = null)
     {
         if ($this->match(
             $this->utf8
-                ? '(([\pL\w_\-\*!"\']|[\\\\].)([\pL\w\-_"\']|[\\\\].)*)'
+                ? '(([\pL\w\x{00A0}-\x{10FFFF}_\-\*!"\']|[\\\\].)([\pL\w\x{00A0}-\x{10FFFF}\-_"\']|[\\\\].)*)'
                 : '(([\w_\-\*!"\']|[\\\\].)([\w\-_"\']|[\\\\].)*)',
             $m,
             $eatWhitespace