Lexing/parsing of CSS pseudos with ident arguments

This allows the lexing/parsing of expressions such as "html:lang(en)".

spec/oga/css/lexer/pseudo_classes_spec.rb

@@ -116,5 +116,15 @@ describe Oga::CSS::Lexer do
         [:T_RPAREN, nil]
       ]
     end
+
+    example 'lex the :lang(fr) pseudo class' do
+      lex_css(':lang(fr)').should == [
+        [:T_COLON, nil],
+        [:T_IDENT, 'lang'],
+        [:T_LPAREN, nil],
+        [:T_IDENT, 'fr'],
+        [:T_RPAREN, nil]
+      ]
+    end
   end
 end

spec/oga/css/parser/pseudo_classes_spec.rb

@@ -107,5 +107,14 @@ describe Oga::CSS::Parser do
         s(:pseudo, 'focus', s(:test, nil, 'x'))
       )
     end
+
+    example 'parse a pseudo class with an identifier as the argument' do
+      parse_css('x:lang(fr)').should == s(
+        :pseudo,
+        'lang',
+        s(:test, nil, 'x'),
+        s(:test, nil, 'fr')
+      )
+    end
   end
 end