Review request for JMC-6274: Adding Eclipse 2018-12 and 2019-03 target platforms.

[Guru]

+1, Tested on Mac OS X, Windows and Linux (Ubuntu). 

Thanks
Guru 
> On 29-Apr-2019, at 3:00 PM, Marcus Hirt <marcus at hirt.se> wrote:
> 
> Hi all,
> 
> Please review this fix to support new Eclipse platforms and switching to
> 2019-03 by default. Also removing Oxygen.
> 
> Jira:   https://bugs.openjdk.java.net/browse/JMC-6274
> Webrev: http://cr.openjdk.java.net/~hirt/JMC-6274/webrev.3/
> 
> Kind regards,
> Marcus
> 
>