RFR: 8242039: Improve jlink VersionPropsPlugin

[Langer, Christoph]

Hi,

please review a small improvement for the jlink VersionPropsPlugin. The Plugin modifies the bytecode of java/lang/VersionProps.class to replace the initializion of certain vendor specific system properties with custom values. This modification currently adds two bytecodes per constant, a pop and another ldc. I overhauled it to simply replace the original ldc of the old value with another ldc, loading the custom value.

I was playing a bit with the plugin and tried to familiarize with the code – so that’s the outcome ��

I also added an @SuppressWarnings("unused") in VersionProps.java.template to quiesce an IDE warning.

Bug: https://bugs.openjdk.java.net/browse/JDK-8242039
Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8242039.0/

Thanks
Christoph