Fetch Scala lib sources from the sources artifacts.

Instead of cloning the git repo. This should make the dbuild build
happy, assuming it does publish the source artifacts.

For partest, we still need to use the git clone strategy, since the
published artifacts do not contain the partest tests (obviously).
Avoid the illusion that new Thread() links.
Implement Throwable.printStackTrace(PrintWriter).
Make java.lang.Void final.
Cleanup java.lang.ref.*.
Update java.lang.reflect.Arrays for Floats.
Merge pull request #1217 from sjrd/fetch-scalalib-src-from-artifact

Fetch Scala lib sources from the sources artifacts.
Merge pull request #1285 from sjrd/review-javalanglib

Complete review of the java.lang.* library
Cleanup java.util.Arrays.

Avoid a lot of duplication by implementing algorithms with
@specialized methods, and inlined lambdas.
Fix line endings in java.util.Date.
Coding style in java.util.Date.
Cleanup java.util.Random.