Add tests on callable references

Object members and accessors for private class members

compiler/testData/codegen/box/callableReference/objectMemberUnitNoArgs.kt

@@ -0,0 +1,13 @@
+object A {
+    var result = "Fail"
+    
+    fun foo() {
+        result = "OK"
+    }
+}
+
+fun box(): String {
+    val x = A::foo
+    A.x()
+    return A.result
+}

compiler/testData/codegen/box/callableReference/objectMemberUnitOneStringArg.kt

@@ -0,0 +1,13 @@
+object A {
+    var result = "Fail"
+    
+    fun foo(newResult: String) {
+        result = newResult
+    }
+}
+
+fun box(): String {
+    val x = A::foo
+    A.x("OK")
+    return A.result
+}

compiler/testData/codegen/box/callableReference/privateClassMember.kt

@@ -0,0 +1,7 @@
+class A {
+    private fun foo() = "OK"
+
+    fun bar() = this.(::foo)()
+}
+
+fun box() = A().bar()