e2fsck started complaining about the upper part of the 48bit value
of file_acl, even on non-linux systems (e.g. the Hurd), where
the additional 16bits do not exist, and are used for other usage
(h_i_mode_high on the Hurd).
This is due to ext2fs_file_acl_block (and ext2fs_file_acl_block_set)
not checking that the fs->super->s_creator_os is EXT2_OS_LINUX before
accessing (or setting) the inode->osd2.linux2.l_i_file_acl_high field.