Fix #133 <unicode-range> parsing corner case

Unexpected tokens after U+<integer> are not an error,
just not part of the <unicode-range>.

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "cssparser"
-version = "0.12.1"
+version = "0.12.2"
 authors = [ "Simon Sapin <simon.sapin@exyr.org>" ]
 
 description = "Rust implementation of CSS Syntax Level 3"

src/css-parsing-tests/urange.json

@@ -55,6 +55,10 @@
     null
 ],
 
+"U+2 , U+???", [
+    [2, 2],
+    [0, 4095]
+],
 
 "u+20-3F, u+3F-3F, u+3F-3E, U+0-110000, U+0-10FFFF, U+100000-2, U+1000000-2, U+10-200000", [
     [32, 63],

src/unicode_range.rs

@@ -82,10 +82,8 @@ fn concatenate_tokens(input: &mut Parser, remaining: &mut &mut [u8]) -> Result<(
             let int_value = positive_integer_with_plus_sign(value)?;
             write!(remaining, "{}", int_value)?;
 
+            let after_number = input.position();
             match input.next_including_whitespace() {
-                // EOF here is fine
-                Err(()) => {},
-
                 Ok(Token::Delim('?')) => {
                     // If `remaining` is already full, `int_value` has too many digits
                     // so we can use `result?` Rust syntax.
@@ -105,7 +103,7 @@ fn concatenate_tokens(input: &mut Parser, remaining: &mut &mut [u8]) -> Result<(
                     write!(remaining, "{}", int_value)?
                 }
 
-                _ => return Err(Error)
+                _ => input.reset(after_number)
             }
         }