Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/properties/kt613.kt

@@ -0,0 +1,15 @@
+package name
+
+class Test() {
+  var i = 5
+  val ten = 10.toLong()
+
+  fun Long.t() = this.toInt() + i++ + ++i
+
+  fun tt() = ten.t()
+}
+
+fun box() : String {
+  var m = Test()
+  return if((m.i)++ == 5 && ++(m.i) == 7 && m.tt() == 26) "OK" else "fail"
+}