RFR: JDK-8224222: Inno setup 6 broke jpackage

[Alexey Semenyuk]

Please review the jpackage fix for bug [1] at [2].

This is a fix for the JDK-8200758-branch branch of the open sandbox
repository (jpackage).

- Improve code detecting version of Inno Setup to make it work with Inno 
Setup v6 updates.

[1] https://bugs.openjdk.java.net/browse/JDK-8224222

[2] http://cr.openjdk.java.net/~asemenyuk/8224222/webrev.00/

Thanks,
Alexey