add required config file (#352)

* add required config file

* add comments to the config.h file as per PR review

Author: danielsn

.cbmc-batch/include/aws/common/config.h

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file 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.
+ */
+
+#pragma once
+
+/* aws-c-common requires a configuration file.
+ * We do not currently need to set any options.
+ */