Handle escapes in string literals.

frog/tests/leg/src/ScannerTest.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #import('../../../../utils/utf8/utf8.dart');
 #import('../../../leg/scanner/scannerlib.dart');
 #import('../../../leg/scanner/scanner_implementation.dart');
+#import('../../../leg/util/characters.dart');
 #source('../../../leg/scanner/byte_strings.dart');
 #source('../../../leg/scanner/byte_array_scanner.dart');
 
 Token scan(List<int> bytes) => new ByteArrayScanner(bytes).tokenize();
 
 bool isRunningOnJavaScript() => 1 === 1.0;
 
 main() {
   // Google favorite: "Îñţérñåţîöñåļîžåţîờñ".
   Token token = scan([0xc3, 0x8e, 0xc3, 0xb1, 0xc5, 0xa3, 0xc3, 0xa9, 0x72,
@@ skipping 26 matching lines @@
 
   if (!isRunningOnJavaScript()) {
     // DESERET CAPITAL LETTER BEE, unicode 0x10412(0xD801+0xDC12)
     // UTF-8: F0 90 90 92
     token = scan([0xf0, 0x90, 0x90, 0x92, $EOF]);
     Expect.stringEquals("𐐒", token.value.toString());
   } else {
     print('Skipping non-BMP character test');
   }
 }