embed to take a maximum value for nsectors.
* include/grub/emu/hostdisk.h (grub_util_ldm_embed): Likewise.
* include/grub/fs.h (grub_fs): Likewise.
* grub-core/partmap/msdos.c (embed_signatures): New array.
(pc_partition_map_embed): Check for and avoid sectors matching any
of the signatures in embed_signatures, up to max_nsectors.
* grub-core/partmap/gpt.c (gpt_partition_map_embed): Restrict
returned sector map to max_nsectors.
* grub-core/disk/ldm.c (grub_util_ldm_embed): Likewise.
* grub-core/fs/btrfs.c (grub_btrfs_embed): Likewise.
* grub-core/fs/zfs/zfs.c (grub_zfs_embed): Likewise.
* util/grub-setup.c (setup): Allow for the embedding area being
split into multiple blocklists. Tell dest_partmap->embed the
maximum number of sectors we care about.