SBT 0.13 build
Remove classes specific to scala/scala

We don't want to depend on scala.tools.asm nor the repl here.
The next commit refactors partest's classpath handling,
so that we can build the files we remove here in the compiler build,
and include the resulting artifacts on the classpath there.
Simplify classpath handling a bit.

It's still utter madness, so -- for an extra sanity check --
I'm printing the banner for every test run.

The classpath used for tests (modulo additions for certain test cases)
is `fileManager.testClassPath` (or `testClassPathUrls`).

Ideally, we should get rid of all this custom logic in FileManager,
and just use COMPILATION_CLASSPATH.