nettle: upgrade 3.7.3 -> 3.8

Changelog:
==========
This release includes a couple of new features, and many
performance improvements. It adds assembly code for two more
architectures: ARM64 and S390x.

The new version is intended to be fully source and binary
compatible with Nettle-3.6. The shared library names are
libnettle.so.8.5 and libhogweed.so.6.5, with sonames
libnettle.so.8 and libhogweed.so.6.

New features:
--------------
* AES keywrap (RFC 3394), contributed by Nicolas Mora.

* SM3 hash function, contributed by Tianjia Zhang.

* New functions cbc_aes128_encrypt, cbc_aes192_encrypt,
  cbc_aes256_encrypt.

  On processors where AES is fast enough, e.g., x86_64 with
  aesni instructions, the overhead of using Nettle's general
  cbc_encrypt can be significant. The new functions can be
  implemented in assembly, to do multiple blocks with reduced
  per-block overhead.

  Note that there's no corresponding new decrypt functions,
  since the general cbc_decrypt doesn't suffer from the same
  performance problem.

Bug fixes:
-------------
* Fix fat builds for x86_64 windows, these appear to never
  have worked.

Optimizations:
----------------
* New ARM64 implementation of AES, GCM, Chacha, SHA1 and
  SHA256, for processors supporting crypto extensions. Great
  speedups, and fat builds are supported. Contributed by
  Mamone Tarsha.

* New s390x implementation of AES, GCM, Chacha, memxor, SHA1,
  SHA256, SHA512 and SHA3. Great speedups, and fat builds are
  supported. Contributed by Mamone Tarsha.

* New PPC64 assembly for ecc modulo/redc operations,
  contributed by Amitay Isaacs, Martin Schwenke and Alastair
  D´Silva.

* The x86_64 AES implementation using aesni instructions has
  been reorganized with one separate function per key size,
  each interleaving the processing of two blocks at a time
  (when the caller processes multiple blocks with each call).
  This gives a modest performance improvement on some
  processors.

* Rewritten and faster x86_64 poly1305 assembly.

Known issues:
-------------
* Nettle's testsuite doesn't work out-of-the-box on recent
  MacOS, due to /bin/sh discarding the DYLD_LIBRARY_PATH
  environment variable. Nettle's test scripts handle this in
  some cases, but currently fails the test cases that are
  themselves written as /bin/sh scripts. As a workaround, use

  make check EMULATOR='env DYLD_LIBRARY_PATH=$(TEST_SHLIB_DIR)'

Miscellaneous:
--------------
* Updated manual to current makeinfo conventions, with no
  explicit node pointers. Generate pdf version with texi2pdf,
  to get working hyper links.

* Added square root functions for NIST ecc curves, as a
  preparation for supporting compact point representation.

* Reworked internal GCM/ghash interfaces, simplifying assembly
  implementations. Deleted unused GCM C implementation
  variants with less than 8-bit lookup table.

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>