8076543: Add @modules as needed to the langtools tests
Reviewed-by: jjg, shurailine

8005282: Use @library tag with non-relative path for javac tests
Reviewed-by: jjg

7025809: Provided new utility visitors supporting SourceVersion.RELEASE_8
Reviewed-by: jjg, mcimadamore

7029150: Project Coin: present union types from the tree API through to javax.lang.model
Reviewed-by: mcimadamore