AbstractTransformer #1419: a type is turned to raw if it has a contravariant tp with Nothing
BoxingVisitor #1419: make sure members/invocations on raw types are marked as erased, invocation on raw types
Decl: squash NPE
ExpressionTransformer: variable is gone ceylon/ceylon.language#334
Updated tests for ceylon/ceylon.language#334: variable is gone
Test for #1419
Test .src: fallout from #1419

Not too sure why...
Added test for #1420: overload tests
Fix for #1422: Interop: lowercase static inner class
Test for #1422: Interop: lowercase static inner class
Removed references to `OSUtil` because it's not available for the bootstrap (ceylon/ceylon-ide-eclipse#747)