backend: Use simple DFS during closure building.

Now closure builder can contain includes. Includes
are another builders which closures must be added
to the building one.
Includes are:

For function closure:
	call targets (including constructors)
	callable reference targets

For class:
	all children declarations
	call targets (including constructors)
        callable reference targets

For constructor:
	call and callable reference targets
	delegating constructor call target
	constructing class closure

backend.native/tests/codegen/innerClass/localFunctionCallFromLocalClass.kt

@@ -1,14 +0,0 @@
-fun main(args : Array<String>) {
-    var x = 1
-    fun local1() {
-        x++
-    }
-
-    class A {
-        fun bar() {
-            local1()
-        }
-    }
-    A().bar()
-    println("OK")
-}