backend/tests:

* enable 'expression_as_statement'
* add unit{1..4}

backend.native/tests/codegen/basics/unit1.kt

@@ -0,0 +1,3 @@
+fun main(args: Array<String>) {
+    println(println("First").toString())
+}

backend.native/tests/codegen/basics/unit2.kt

@@ -0,0 +1,8 @@
+fun main(args: Array<String>) {
+    val x = foo()
+    println(x.toString())
+}
+
+fun foo() {
+    return Unit
+}

backend.native/tests/codegen/basics/unit3.kt

@@ -0,0 +1,7 @@
+fun main(args: Array<String>) {
+    foo(Unit)
+}
+
+fun foo(x: Any) {
+    println(x.toString())
+}

backend.native/tests/codegen/basics/unit4.kt

@@ -0,0 +1,37 @@
+fun main(args: Array<String>) {
+    for (x in 0 .. 8) {
+        foo(x, Unit)
+    }
+    println("Done")
+}
+
+var global = 42
+
+fun foo(x: Int, unit: Unit) {
+    var local = 5
+    val y: Unit = when (x) {
+        0 -> {}
+        1 -> local = 6
+        2 -> global = 43
+        3 -> unit
+        4 -> Unit
+        5 -> bar()
+        6 -> return
+        7 -> {
+            5
+            bar()
+        }
+        8 -> {
+            val z: Any = Unit
+            z as Unit
+        }
+        else -> throw Error()
+    }
+
+    if (y !== Unit) {
+        println("Fail at x = $x")
+    }
+}
+
+fun bar() {
+}