Do not reference object's toString result in exception messages

Since we put object's hash code in toString, we end up in putting
non-stable hash code to constant table, which leads to unstable
binaries.

 #KTI-1193 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/OwnerKind.kt

@@ -20,7 +20,7 @@ enum class OwnerKind {
         fun getMemberOwnerKind(descriptor: DeclarationDescriptor): OwnerKind = when (descriptor) {
             is PackageFragmentDescriptor -> PACKAGE
             is ClassDescriptor -> IMPLEMENTATION
-            else -> throw AssertionError("Unexpected declaration container: $this")
+            else -> throw AssertionError("Unexpected declaration container: $descriptor")
         }
     }
 }