HEADS-UP: JDK 8u40 to become the minimum version needed to build FX 8u-dev (and 9)

[Kevin Rushforth]

As a heads-up, I plan to push the fix for the following issue some time 
this week:

[1] RT-40691 : Update the JDK version used to build FX to JDK 8u40

Once pushed, the check for the minimum version JDK will fail unless the 
JDK version is at least 8u40-b26 (meaning 8u45 or 8u60 will be fine as 
well).

This will allow us to remove some workarounds that we currently have for 
Swing bugs that are fixed on the JDK side in 8u40, and will also allow 
us to run unit tests that we have disabled when running on earlier builds.

Please update your JDK to a minimum of 8u40 in order to continue to 
build FX after this fix goes in.

-- Kevin

[1] https://javafx-jira.kenai.com/browse/RT-40691