RFR: 8211450: UndetVar::dup is not copying the kind field to the duplicated instance

[Vicente Romero]

Please review the fix for [1] at [2]. The issue boiled down to 
UndetVar::dup not copying all the fields to the new instance. In this 
case the kind field. This provoked that the special logic that applies 
to thrown type variables was not kicking in and thus thrown variables 
were not being instantiated to RuntimeException. This was provoking flow 
analysis to complain later on.

Thanks,
Vicente

[1] https://bugs.openjdk.java.net/browse/JDK-8211450
[2] http://cr.openjdk.java.net/~vromero/8211450/webrev.00/