++
Create JetTypeBindingTest
++ AbstractJetTypeBindingTest.kt
Create VarianceChecker
Add VarianceChecker to TopDownAnalyzer
Add test (recursive resolve in property declaration) to JetPsiChecker
Added Variance tests
Add receiver to Visibility#isVisible
Change usage "v == Visibilities.PRIVATE" to Visibilities.isPrivate(v)
Fix protected visibility in class object.
Create PRIVATE_TO_THIS visibility
Add serialization for PRIVATE_TO_THIS
~~ draft
Fix completion for private_to_this.
++ TypeBinding.kt
~draft