KT-3503 Can't navigate to implementation of kotlin functions

#KT-3503 Fixed

idea/testData/navigation/implementations/FunctionOverrideNavigation.kt

@@ -0,0 +1,21 @@
+package testing
+
+open class Base {
+    open fun <caret>test() {
+    }
+}
+
+open class SubBase: Base() {
+    override fun test() {
+
+    }
+}
+
+class SubSubBase: SubBase() {
+    override fun test() {
+    }
+}
+
+
+// REF: (in testing.SubBase).test()
+// REF: (in testing.SubSubBase).test()