Added some corner tests on escape analysis

backend.native/tests/runtime/memory/escape1.kt

@@ -0,0 +1,14 @@
+class B(val s: String)
+
+class A {
+    val b = B("zzz")
+}
+
+fun foo(): B {
+    val a = A()
+    return a.b
+}
+
+fun main(args: Array<String>) {
+    println(foo().s)
+}

backend.native/tests/runtime/memory/escape2.kt

@@ -0,0 +1,23 @@
+class A(val s: String)
+
+class B {
+    var a: A? = null
+}
+
+class C(val b: B)
+
+fun foo(c: C) {
+    c.b.a = A("zzz")
+}
+
+fun bar(b: B) {
+    val c = C(b)
+    foo(c)
+}
+
+val global = B()
+
+fun main(args: Array<String>) {
+    bar(global)
+    println(global.a!!.s)
+}