Initial s390-tools-2.0.0 import

This commit is based on the s390-tools-1.39.0 version.

Changes on top of s390-tools-1.39.0:

 - Add MIT license to all source files
 - Add LICENSE file
 - Transform REAMDE to README.md (markdown)
 - Add AUTHORS.md file
 - Add CONTRIBUTING.md file
 - Move changelog from README to CHANGELOG.md file

Reviewed-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>

dump2tar/include/idcache.h

@@ -0,0 +1,26 @@
+/*
+ * dump2tar - tool to dump files and command output into a tar archive
+ *
+ * Caches for user and group ID lookups
+ *
+ * Copyright IBM Corp. 2016, 2017
+ *
+ * s390-tools is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#ifndef IDCACHE_H
+#define IDCACHE_H
+
+#include <stdlib.h>
+#include <sys/types.h>
+
+/* Buffer sizes for getpwuid_r and getgid_r calls (bytes) */
+#define PWD_BUFFER_SIZE	4096
+#define GRP_BUFFER_SIZE	4096
+
+void uid_to_name(uid_t uid, char *name, size_t len);
+void gid_to_name(gid_t gid, char *name, size_t len);
+void idcache_cleanup(void);
+
+#endif /* IDCACHE_H */