Weld build with JDK 9

We should investigate what needs to be done in order to make Weld build and tests work with JDK 9.

This issue is expected to spawn a series of subtasks.

The idea is to push these changes into master branch and once we get the whole picture, we will transfer those changes onto 2.3 branch.

So far these problems were encountered:

• Weld SE and Groovy
  • Groovy compilation fails and it seems there is no way to fix that now on our side
  • We can exclude Groovy compilation in automatically activated profile for now
• Maven checkstyle problems
  • Addressed by WELD-2149
• Test failures
  • So far it seems they might be related to Arquillian tests -> affects tests which trigger use of our Multimap implementation
  • A lot of ConcurrectModificationException thrown randomly when executing tests
  • FormatsTest fails due to BCEL classes being internal-access only
  • JBoss TCK Runner fails with CNFE - can be fixed by adding a dependency, we need to read up on that

IMPORTATNT NOTE!
Currently there are two different JDK 9 EA distributions you can download - with and without project Jigsaw (modular approach). We should test it with both.
Current observation suggests that there is no difference in using either (same things fails/succeed) but keep an eye out on that.