Support "::foo" as a short-hand for "this::foo"

#KT-15667 Fixed

compiler/testData/diagnostics/tests/callableReference/function/innerConstructorFromClass.kt

@@ -1,12 +1,14 @@
 // !CHECK_TYPE
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
+// !LANGUAGE: +CallableReferencesToClassMembersWithEmptyLHS
+
 import kotlin.reflect.KFunction1
 
 class A {
     inner class Inner
     
     fun main() {
-        ::<!CALLABLE_REFERENCE_TO_MEMBER_OR_EXTENSION_WITH_EMPTY_LHS!>Inner<!>
+        ::Inner
         val y = A::Inner
 
         checkSubtype<KFunction1<A, Inner>>(y)