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/kt2626.kt

@@ -0,0 +1,10 @@
+package example2
+
+fun box() = Context.OsType.OK.toString()
+
+object Context
+{
+        public enum class OsType {
+                WIN2000; WINDOWS; MACOSX; LINUX; OTHER; OK
+        }
+}