Move blackBoxFile() testData to box/ directory

Delete all test methods (and empty test classes), since they'll be
auto-generated

compiler/testData/codegen/box/classes/kt1611.kt

@@ -0,0 +1,11 @@
+fun box(): String {
+    return Foo().doBar("OK")
+}
+
+class Foo() {
+    val bar : (str : String) -> String = { it }
+
+    fun doBar(str : String): String {
+        return bar(str);
+    }
+}