sfdisk: make unhiding as complete as possible

It is unlikely anyone will ever need this, but I like idea commands being
complete.  The partition id's that can be unhide after this change are;

Hidden HPFS/NTFS
Hidden W95 FAT32
Hidden W95 FAT32 (LBA)
Hidden W95 FAT16 (LBA)

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
docs: add missing options to sfdisk manual

And improve what is said about four of the dangerous options.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
include: copy unlocked-io.h from gnulib

At the moment util-linux command are not threading, which means they can
safely use thread-unsafe IO system calls which should make printing
quicker.

References: http://marc.info/?l=util-linux-ng&m=137266928927642&w=3
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
hexdump: use unlocked io, and avoid use of printf()

This makes common cases about 35-50% quicker.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
text-utils: use unlocked io

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
misc-utils: use unlocked io

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
scriptreplay: use unlocked io

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
dmesg: use unlocked io, and avoid use of printf()

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
utmpdump: use unlocked io, and avoid use of printf()

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
dmesg: inform user --show-delta and iso8601 time format does not mix

References: http://marc.info/?l=util-linux-ng&m=137267606929951&w=2
Signed-off-by: Sami Kerola <kerolasa@iki.fi>