Scala 2.10/2.11 cross compatibility for a test

In Scala 2.11, the presentation compiler will no longer
see macro expansions in trees. Instead, it will see the
expandee (e.g. `StringContext("").f()`, attributed with
the type of the expansion.

The output of one test in `CompilationUnitDependenciesTest`
will change as result of this.

Review by @misto