Supported SAM constructors in codegen (simplest case).

compiler/testData/codegen/box/sam/runnable.kt

@@ -0,0 +1,7 @@
+var result = "FAIL"
+
+fun box(): String {
+    val r = Runnable { result = "OK" }
+    r.run()
+    return result
+}

compiler/testData/codegen/box/sam/runnableAccessingClosure1.kt

@@ -0,0 +1,8 @@
+fun box(): String {
+    val o = "O"
+    var result = ""
+
+    val r = Runnable { result = o + "K" } //capturing local vals and local var
+    r.run()
+    return result
+}

compiler/testData/codegen/box/sam/runnableAccessingClosure2.kt

@@ -0,0 +1,11 @@
+class Box(val s: String) {
+    fun extract(): String {
+        var result = ""
+        Runnable { result = s }.run() // capturing this and local var
+        return result
+    }
+}
+
+fun box(): String {
+    return Box("OK").extract()
+}