Frog: Fix parsing of hex literals with >31 bits

frog/frogsh

Index: frog/frogsh
diff --git a/frog/frogsh b/frog/frogsh
index d93d028a2501514fa2a32656eaec6fd1adf8f7e0..85f4b548dc193ed587738f276afb7886dce86038 100755
--- a/frog/frogsh
+++ b/frog/frogsh
@@ -19874,7 +19874,7 @@ lang_Parser.parseHex = function(hex) {
    i < hex.length; i++) {
     var digit = lang_Parser._hexDigit(hex.charCodeAt(i));
     $assert($ne(digit, -1), "digit != -1", "parser.dart", 1339, 14);
-    result = (result << 4) + $assert_num(digit);
+    result = (result * 16) + $assert_num(digit);
   }
   return $assert_num(result);
 }