MFC of 276737, 322200, 322201, 322271, and 322297

276737: Remove old ioctl use and support
322200: Remove (broken) search for alternate superblocks
322201: Show differences when alternate superblock fails to match
322271: Cleanup for 322200.
322297: Restore fsck_ffs ability to find alternate superblocks

Discussed with: kib, imp
Differential Revision: https://reviews.freebsd.org/D11589
Approved by: re (kib)

MFC r267355:
Add UUIDs for DragonFlyBSD's partition types.

MFC r267356:
Add DragonFlyBSD's Hammer FS types and type names.

MFC r267357:
Add aliases for DragonFlyBSD's partition types.

MFC r267358:
Allow dumping to DragonFlyBSD's swap partition.

MFC r267359:
Add disklabel64 support to GEOM_PART class.

This partitioning scheme is used in DragonFlyBSD. It is similar to
BSD disklabel, but has the following improvements:
* metadata has own dedicated place and isn't accessible through partitions;
* all offsets are 64-bit;
* supports 16 partitions by default (has reserved place for more);
* has reserved place for backup label (but not yet implemented);
* has UUIDs for partitions and partition types;

MFC r267360:
Add disklabel64 support

Relnotes: yes

MFC r267355:
Add UUIDs for DragonFlyBSD's partition types.

MFC r267356:
Add DragonFlyBSD's Hammer FS types and type names.

MFC r267357:
Add aliases for DragonFlyBSD's partition types.

MFC r267358:
Allow dumping to DragonFlyBSD's swap partition.

MFC r267359:
Add disklabel64 support to GEOM_PART class.

This partitioning scheme is used in DragonFlyBSD. It is similar to
BSD disklabel, but has the following improvements:
* metadata has own dedicated place and isn't accessible through partitions;
* all offsets are 64-bit;
* supports 16 partitions by default (has reserved place for more);
* has reserved place for backup label (but not yet implemented);
* has UUIDs for partitions and partition types;

MFC r267360:
Add disklabel64 support

Relnotes: yes