update visualvm to 2.1.8

Changes:

• import 2.1.6
• import 2.1.8

Testing:

• ppa build [2]
• manual testing:
  • 
  • 

[1] https://github.com/openjdk/nashorn

[2] https://launchpad.net/~vpa1977/+archive/ubuntu/october-21/+sourcepub/15931640/+listing-archive-extra