backend/tests: Add blackbox tests from Kotlin JVM

Added tests from testData/codegen/box directory. There are blackbox tests
in other directories and they are to be added.

backend.native/tests/external/codegen/blackbox/enum/inclassobj.kt

@@ -0,0 +1,15 @@
+fun box() = if(Context.operatingSystemType == Context.Companion.OsType.OTHER) "OK" else "fail"
+
+public class Context
+{
+        companion object
+        {
+                public enum class OsType {
+                        LINUX,
+                        OTHER;
+                }
+
+                public val operatingSystemType: OsType
+                        get() = OsType.OTHER
+        }
+}