BenchmarkDotNet: added NamespacePatch.cs file to define namespaces th…

…at didn't exist in old versions of Lucene.NET

src/Lucene.Net.Tests.BenchmarkDotNet/Util/NamespacePatch.cs

@@ -0,0 +1,21 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+// Didn't exist in early versions of Lucene.NET - this is just to patch those cases so using directives will compile
+namespace Lucene.Net.Documents.Extensions
+{
+}