src/t_dir_type: support filtering by inode number

usage: t_dir_type <dir> <inode number>

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

doc/auxiliary-programs.txt

@@ -18,6 +18,7 @@ Contents:
  - af_unix		-- Create an AF_UNIX socket
  - open_by_handle	-- open_by_handle_at syscall exercise
  - stat_test		-- statx syscall exercise
+ - t_dir_type		-- print directory entries and their file type
  - xfs_io		-- General I/O operation exercise
 
 
@@ -48,6 +49,12 @@ stat_test
 		_require_statx
 
 
+t_dir_type
+
+	The t_dir_type program exercises the getdents64() system call.
+	It prints directory entry names returned from getdents64() and
+	thier d_type, optionally filtered by type or by inode number.
+
 xfs_io
 
 	The xfs_io program can be found in the xfsprogs package and can be used