Add missing copyright headers

dev/core/src/com/google/gwt/dev/jjs/impl/SplitCaseStatementValues.java

@@ -1,3 +1,18 @@
+/*
+ * Copyright 2024 GWT Project Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
 package com.google.gwt.dev.jjs.impl;
 
 import com.google.gwt.dev.jjs.ast.*;