Ensure that the "skipFinallyBlock" variable is set even if CatchBlock is null

[kpreisser]

Follow-Up commit for c773bf2:
Generate a catch block even if this.CatchClause is null (and rethrow the exception in this case), to ensure the skipFinallyBlock variable is set in every case, not only when the script has a catch clause. This fixes the remaining issue of #85 where a finally block would execute if the script only has a try-finally block instead of try-catch-finally and the Exception is not catchable in JS.

Notes:

• Currently, the TryFinallyStatement generates a catch (Exception ex) clause. In theory, the CLR allows to throw any object, nut just Exception, so to be safe we might want to change the emit to catch (object o) and change ScriptEngine.CanCatchException(Exception) to accept an object parameter.
• I think the skipFinallyBlock variable could be changed to use a temporary variable.

Thanks!

[paulbartrum]

I added some unit tests, but otherwise merged your changes in wholesale. Thanks! :-)