HEADS-UP: Proposal to bump the minimum boot JDK for FX to JDK 10

[Kevin Rushforth]

As mentioned in another thread [1] we should update the minimum boot JDK 
used to build FX to 10, which will allow the use of JDK 10 langauge 
features, such as 'var', as well as JDK 10 APIs. It's also the right 
time to do this in general. I filed a new RFE [2] to track this and plan 
to send it out for review next week.

Please let me know if there are any concerns. We already use JDK 10 to 
build FX 11 ea bits. I presume that the travis and appveyor CI builds of 
the github mirror do the same?

-- Kevin

[1] 
http://mail.openjdk.java.net/pipermail/openjfx-dev/2018-March/021671.html

[2] https://bugs.openjdk.java.net/browse/JDK-8200446