[parser] implement error reporting for Scanner errors

test/message/unicode-escape-invalid.js

Index: test/message/unicode-escape-invalid.js
diff --git a/test/message/regress/regress-4829-1.js b/test/message/unicode-escape-invalid.js
similarity index 82%
copy from test/message/regress/regress-4829-1.js
copy to test/message/unicode-escape-invalid.js
index 1ad5feda8cb96cd24e4c47f7407c9699d150c327..5378acf816b8e17cae96b2a13ed79ad8dc0f49e3 100644
--- a/test/message/regress/regress-4829-1.js
+++ b/test/message/unicode-escape-invalid.js
@@ -2,6 +2,4 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-function tag() {}
-
-tag(tag`\xyy`);
+print("\u{FFYZ}");