Revert "SI-6426, importable _."

This reverts commit d2316df920ffa4804fe51e8f8780240c46efa982.

We can't make `_` an illegal identifier -- it's legal in Java,
so we must be able to name these Java underscores.
Merge pull request #3253 from retronym/ticket/8062

 Fix inliner cycle with recursion, separate compilation
Merge pull request #3261 from adriaanm/ticket-6426

Revert ", importable _."
Partially revert f8d8f7d08d.

Need `${dist.dir}/lib/scala-partest.jar` for maven publish.

We still don't want to distribute it in the distribution,
but will have to remove it in release script, as 2.10.x's
build hasn't been refactoreded like master's, and I'm not backporting it.
Report error on code size overflow, log method name.

We used to silently skip class files that would exceed the JVM's size limits.
While rare, this should still be an error.

While I was at it, also included the name of the offending method.
Merge pull request #3268 from adriaanm/support-3021

Report error on code size overflow, log method name.
Test demonstrating SI-8085

* The presentation compiler sourcepath is now correctly set-up.
* Amazingly enough (for me at least), the outer import in the
  package object seem to be responsible of the faulty behavior.
  In fact, if you move the import clause *inside* the package object,
  the test succeed!
  The test's output does provide the correct hint of this:

```
% diff /Users/mirco/Projects/ide/scala/test/files/presentation/t8085-presentation.log /Users/mirco/Projects/ide/scala/test/files/presentation/t8085.check
@@ -1,3 +1,2 @@
 reload: NodeScalaSuite.scala
-prefixes differ: <empty>.nodescala,nodescala
-value always is not a member of object scala.concurrent.Future
+Test OK
```

Notice the ``-prefixes differ: <empty>.nodescala,nodescala``. And compare
it with the output when the import clause is placed inside the package
object:

```
% diff /Users/mirco/Projects/ide/scala/test/files/presentation/t8085-presentation.log /Users/mirco/Projects/ide/scala/test/files/presentation/t8085.check
@@ -1,4 +1,2 @@
 reload: NodeScalaSuite.scala
-reload: NodeScalaSuite.scala
-open package module: package object nodescala
 Test OK
```

Notice now the ``-open package module: package object nodescala``!
SI-8085 Fix BrowserTraverser for package objects

A source file like:

    import foo.bar
    package object baz

Is parsed into:

    package <empty> {
       import foo.bar
       package baz {
          object `package`
       }
    }

A special case in Namers compensates by adjusting the owner of
`baz` to be `<root>`, rather than `<empty>`.

This wasn't being accounted for in `BrowserTraverser`, which
underpins `-sourcepath`, and allows the presentation compiler to
load top level symbols from sources outside those passes as
the list of sources to compile.