Regression: Lifted inner method tries to use this

[smarter]

This is exactly the same issue than #545, it was fixed in b0856fe but in the same pull request 32a7004 caused a regression.
In the example from #545, the enclosing class is the module class Test$ and the top class is also the module class Test$, so the test encClass.isProperlyContainedIn(topClass) fails.

Assigned to @DarkDimius .

[odersky]

The fix causes the build to fail. ClassPath does not compile anymore. This is what I have been seeing all along. It shows the value of a test infrastructure we can rely on. Without it we are flying blind.