Allow LANGUAGE_VERSION directive in codegen tests

compiler/tests-common/org/jetbrains/kotlin/codegen/CodegenTestCase.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
+ * Copyright 2010-2016 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -163,7 +163,8 @@ public abstract class CodegenTestCase extends KtUsefulTestCase {
         }
 
         if (explicitLanguageVersion != null) {
-            // configuration.put(CommonConfigurationKeys.LANGUAGE_VERSION_SETTINGS, new LanguageVersionSettingsImpl(explicitLanguageVersion));
+             configuration.put(CommonConfigurationKeys.LANGUAGE_VERSION_SETTINGS,
+                               new LanguageVersionSettingsImpl(explicitLanguageVersion, ApiVersion.LATEST));
         }
 
         updateConfigurationWithFlags(configuration, kotlinConfigurationFlags);