Add NullFS

Signed-off-by: Thomas Heijligen <src@posteo.de>
diff --git a/src/vfs.c b/src/vfs.c
index 03e9374..f4c7851 100644
--- a/src/vfs.c
+++ b/src/vfs.c
@@ -11,6 +11,7 @@
 	int (*dir_func) (char *dirname);
 	int (*close_func) (void);
 } static const fsys_table[] = {
+	{ "nullfs", nullfs_mount, nullfs_read, nullfs_dir, NULL },
 	{ "ext2", ext2fs_mount, ext2fs_read, ext2fs_dir, NULL },
 	{ "iso9660", iso9660_mount, iso9660_read, iso9660_dir, NULL },
 };