Review request for JMC-6277: Supporting new JavaFX 12 events

[Guru]

1. Please update “JfxVersionUtil.java” with copyright header. 

2. (Not a must) Nit : JavaFxEventAvailability.JavaFx12 to JavaFxEventAvailability.OpenJFXModule or JavaFxEventAvailability.JavaFxModule 
We can encounter None(Which I believe its for idk9, 10 and 11) , Javafx from JDK 8, and JavaFx12 (i.e OpenJfx which is based on version 12 and above). 

Other than the above, others changes looks good to me. 

Thanks,
Guru
> On 08-Jan-2019, at 2:52 AM, Marcus Hirt <marcus.hirt at oracle.com> wrote:
> 
> Hi all,
> 
> Please review this fix to support the new JavaFX 12 events.
> See:    https://bugs.openjdk.java.net/browse/JDK-8088418
> 
> Included are also some fixes for minor warnings and mounting
> the metadata and g1 optional pages plug-ins in better places.
> 
> Jira:   https://bugs.openjdk.java.net/browse/JMC-6277
> Webrev: http://cr.openjdk.java.net/~hirt/JMC-6277/webrev.01/
> 
> Kind regards,
> Marcus
> 
> 
> 
> 
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