Support for cbfs. Also factor out the part which is common

for all archives to a separate module. This splits tar from cpio
	as they are very different but keeps cpio, cpio_be, odc and newc
	together since they're very similar.

grub-core/fs/newc.c

@@ -65,7 +65,6 @@ read_number (const char *str, grub_size_t size)
 GRUB_MOD_INIT (newc)
 {
   grub_fs_register (&grub_cpio_fs);
-  my_mod = mod;
 }
 
 GRUB_MOD_FINI (newc)