Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC 271881: Fix partition alignment and image rounding when any of
-P (block size), -T (track size) or -H (number of heads) is given.

Approved by: re@ (gjb)

MFC r268236,268264,268524,268646,268802,269021:
This brings VHD support to mkimg(1); both dynamic and fixed file formats.
Dynamic VHD and VMDK file images are now sparsely written, meaning that
"free" sectors do not occupy space.

Relnotes: yes

MFC mkimg(1) -- revisions 268159, 268134, 266556, 266514, 266513,
266512, 266511, 266510, 266509, 266176, 265468, 265467,
265462, 265170, 263926, 263924, 263923, 263919 and 263918.

Revision 267182 changed mkimg.1 alongside other unrelated manpages.
The change to mkimg.1 has been applied without registering a merge
of the revision. This allows a future merge of r267182 to happen.

Relnotes: yes

Add mkimg, a utility for making disk images from raw partition contents.
The partitioning scheme can be one of the schemes supported by gpart.

Reviewed by: sjg
Obtained from: Juniper Networks, Inc.

1. When calculating block addresses, round to the physical block
size.
2. Replace scheme_first_block() & scheme_next_block() with
scheme_metadata(). When we round to block sizes, we can't
reliably fixup any miscalculations.
3. In scheme_write, calculate ncyls (number of cyclinders), based
on the total size, sectors/track and number of heads.
4. Add verbosity when constructing the partitions. This includes
the starting block address and size in bytes and blocks.
5. Add verbosity about the sectors/track and number of heads.

1. Add -v option to increase vebosity levels
2. Fix copy-paste bug -- acrually check secsz for being a power of 2
3. Check secsz and blksz parameters
4. Print the sector and block size when -v is given

First batch of media control:
1. Change -h to -H and change -t to -T. Use -H to specify the number of
heads and -T to specify the track size (number of sectors per track).
2. Add -S and -P. Use -S to specify the logical sector size and -P to
specify the physical sector size.

Default to 512 for both the logical and physical sector size.
Set nheads and nsecs to 1 by default.

Revamp:
1. Make secsz globally visible.
2. Have all code use the global secsz and nparts, rather than passing
them around.
3. Introduce lba_t as the type to use when talking about block addresses.
4. Work on LBAs instead of offsets. There's just too much division with
the sector size and there's really no value to use by offsets other
than that is what lseek() wants. For that we now have mkimg_seek().

The bigger picture is that geometry (cylinders, heads, sectors/track) and
also a possible physical sector size are to be globals that can be used
from anyway. We really don't want to pass all that stuff as arguments to
functions and then add __unused for most of them...

Add support for partition labels and write them for GPT.

Dump my WIP of write support for GPT. This compiles, appears to be
complete, but isn't accepted by g_part_gpt. Time to debug and fix.

Add a scheme-specific write callback to write the metadata.
While here:
1. Move FreeBSD-specific headers to a more centralized place, so that
it's easier to port mkimg.
2. Remove inclusion of <uuid.h> where we don't need it (copy-pasted).
3. Check the partition data given on the command line before we do any
I/O.
4. Add scheme_round() for rounding the partition size.
5. Have scheme_write call the scheme-specific write callback and have
it propagate errors back to the caller.

Check the partition type alias as defined by the scheme.

Add mkimg.h. It contains the 'part' structure definition and the linked
list (STAILQ) so that it can be shared and re-used in all source files.
Replace the now unneeded scheme_add_part() with scheme_check_part() for
posterity.

Also (should have been a separate commit), remove the enforcement of
creating a GPT table with at least 128 entries. While this is generally
advised as the default or minimum, it's not actually a hard requirement.
We now recreate a table that's precisely enough (rounded of course).

WHile