Make pointcut pick up subclasses of ScalaJavaBuilder.

This fixes a problem at a customer (cleaning output folders, leading to
empty output folders after successful builds), but I could not reproduce
locally. Confirmed it works for said customer, so rolling back to main
project.

Fixed #1001995

(cherry picked from commit bcd85b3a3af3b00b3cb195b2561c1c880feac0b9)
Merge pull request #604 from adriaanm/modularize

Catch up with Scala Library Modularization.
Don't skip trees with transparent positions when looking for references

Trees with a transparent position may contain trees with range
positions, hence we should make sure to:

1) Traverse tree with a transparent position, and
2) Only call `report` on tree that have an opaque range position.

This is a bug that was made apparent by the changes needed to fix the
Scala compiler ticket SI-4287.
Merge pull request #606 from dotta/issue/si-4287

Don't skip trees with transparent positions when looking for references
Merge pull request #600 from dragos/issue/pointcut-allow-subclasses-1001995

Make pointcut pick up subclasses of ScalaJavaBuilder.