[css-syntax] Revert <unicode-range> changes from CSS 2.1

Author: SimonSapin

css-syntax/Diagrams.src.html

@@ -63,6 +63,8 @@ <h3>Parsing</h3>
 add('whitespace', Diagram(Choice(
 	0, 'space', '\\t', NonTerminal('newline'))));
 
+add('hex digit', Diagram(NonTerminal('0-9 a-f or A-F')));
+
 add('escape', Diagram(
 	'\\', Choice(0,
 		NonTerminal('not newline or hex digit'),
@@ -151,15 +153,10 @@ <h3>Parsing</h3>
 		'U',
 		'u'),
 	'+',
-	Choice(0,
-		Sequence(OneOrMore(NonTerminal('hex digit'), Comment('1-6 times'))),
-		Sequence(
-			ZeroOrMore(NonTerminal('hex digit'), Comment('1-5 times')),
-			OneOrMore('?', Comment('1 to (6 - digits) times'))),
-		Sequence(
-			OneOrMore(NonTerminal('hex digit'), Comment('1-6 times')),
-			'-',
-			OneOrMore(NonTerminal('hex digit'), Comment('1-6 times'))))));
+	Sequence(OneOrMore(Choice(0, NonTerminal('hex digit'), '?'), Comment('1-6 times'))),
+	Optional(Sequence(
+		'-',
+		OneOrMore(NonTerminal('hex digit'), Comment('1-6 times'))))));
 
 add('〈include-match〉', Diagram('~='));