Conform functions to extension functions and vice versa

#KT-5989 Fixed

compiler/testData/codegen/boxWithStdlib/callableReference/function/toString.kt

@@ -1,23 +0,0 @@
-fun foo(s: String) {}
-
-class A {
-    fun bar(): String = ""
-}
-
-fun A.baz(x: Int) {}
-
-
-fun box(): String {
-    val f = "${::foo}"
-    if (f != "kotlin.reflect.KFunction1<java.lang.String, kotlin.Unit>") return "Fail foo: $f"
-
-    val nameOfA = (A() as java.lang.Object).getClass().getName()
-
-    val g = "${A::bar}"
-    if (g != "kotlin.reflect.KMemberFunction0<$nameOfA, java.lang.String>") return "Fail bar: $g"
-
-    val h = "${A::baz}"
-    if (h != "kotlin.reflect.KExtensionFunction1<$nameOfA, java.lang.Integer, kotlin.Unit>") return "Fail baz: $h"
-
-    return "OK"
-}