Unused constructor removed
Abstract class mrged with its only subclass
Package private fixed by providing equals() on package views
Fix multifile/singlefile packages
Better diagnostics in CompilationException
Fix environments/jetFile creation in LineNumberTest
Assertion added
++ to Write reference targets for names in package headers
++ JetTestUtils.createFile()
Migrate tests to TestCoreEnvironment
Usages of resolveNamespace() removed from tests