MFC r311655: libmd: add noexec stack annotation in skein_block_asm.s

Sponsored by: The FreeBSD Foundation

MFC r307521: libmd: introduce functions that operate on fd instead of filename

MFC r307584

Fix C++ includability of crypto headers with static array sizes

C99 allows array function parameters to use the static keyword for their
sizes. This tells the compiler that the parameter will have at least the
specified size, and calling code will fail to compile if that guarantee is
not met. However, this syntax is not legal in C++.

This commit reverts r300824, which worked around the problem for
sys/sys/md5.h only, and introduces a new macro: min_size(). min_size(x) can
be used in headers as a static array size, but will still compile in C++
mode.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Connect the SHA-512t256 and Skein hashing algorithms to ZFS

Support for the new hashing algorithms in ZFS was introduced in r289422
However it was disconnected because FreeBSD lacked implementations of
SHA-512 (truncated to 256 bits), and Skein.

These implementations were introduced in r300921 and r300966 respectively

This commit connects them to ZFS and enabled these new checksum algorithms

This new algorithms are not supported by the boot blocks, so do not use them
on your root dataset if you boot from ZFS.

Relnotes: yes
Sponsored by: ScaleEngine Inc.

Import the skein hashing algorithm, based on the threefish block cipher

Connect it to userland (libmd, libcrypt, sbin/md5) and kernel (crypto.ko)

Support for skein as a ZFS checksum algorithm was introduced in r289422
but is disconnected because FreeBSD lacked a Skein implementation.

A further commit will enable it in ZFS.

Reviewed by: cem
Sponsored by: ScaleEngine Inc.
Differential Revision: https://reviews.freebsd.org/D6166

Import Skein 1.3

Bruce Schneier's hashing algorithm

Used by newer versions of ZFS