* LICENSES: Add 'cipher/keccak-amd64-avx512.S'.
* configure.ac: Add 'keccak-amd64-avx512.lo'.
* cipher/Makefile.am: Add 'keccak-amd64-avx512.S'.
* cipher/keccak-amd64-avx512.S: New.
* cipher/keccak.c (USE_64BIT_AVX512, ASM_FUNC_ABI): New.
[USE_64BIT_AVX512] (_gcry_keccak_f1600_state_permute64_avx512)
(_gcry_keccak_absorb_blocks_avx512, keccak_f1600_state_permute64_avx512)
(keccak_absorb_lanes64_avx512, keccak_avx512_64_ops): New.
(keccak_init) [USE_64BIT_AVX512]: Enable x86-64 AVX512 implementation
if supported by HW features.
--

Benchmark on Intel Core i3-1115G4 (tigerlake):

Before (BMI2 instructions):
                |  nanosecs/byte   mebibytes/sec   cycles/byte  auto Mhz
 SHA3-224       |      1.77 ns/B     540.3 MiB/s      7.22 c/B      4088
 SHA3-256       |      1.86 ns/B     514.0 MiB/s      7.59 c/B      4089
 SHA3-384       |      2.43 ns/B     393.1 MiB/s      9.92 c/B      4089
 SHA3-512       |      3.49 ns/B     273.2 MiB/s     14.27 c/B  ...