Merge upstream JDK master into openjdk/shenandoah master?

[Roman Kennke]

Hello Kelvin & William & all,

it is nice to see progress happening to the generational Shenandoah 
project. However, the baseline JDK version seems a bit old by now. What 
do you think about merging mainline JDK master into openjdk/shenandoah 
master soon? If yes, do you want me to do it, or do you think it's 
better that you do it (because you probably know better how to deal with 
conflicts)?

Cheerio,
Roman