Optimize Keccak 64-bit absorb functions

* cipher/keccak.c [USE_64BIT] [__x86_64__] (absorb_lanes64_8)
(absorb_lanes64_4, absorb_lanes64_2, absorb_lanes64_1): New.
* cipher/keccak.c [USE_64BIT] [!__x86_64__] (absorb_lanes64_8)
(absorb_lanes64_4, absorb_lanes64_2, absorb_lanes64_1): New.
[USE_64BIT] (KECCAK_F1600_ABSORB_FUNC_NAME): New.
[USE_64BIT] (keccak_absorb_lanes64): Remove.
[USE_64BIT_SHLD] (KECCAK_F1600_ABSORB_FUNC_NAME): New.
[USE_64BIT_SHLD] (keccak_absorb_lanes64_shld): Remove.
[USE_64BIT_BMI2] (KECCAK_F1600_ABSORB_FUNC_NAME): New.
[USE_64BIT_BMI2] (keccak_absorb_lanes64_bmi2): Remove.
* cipher/keccak_permute_64.h (KECCAK_F1600_ABSORB_FUNC_NAME): New.

Optimize 64-bit absorb functions for small speed-up. After this
change, 64-bit BMI2 implementation matches speed of fastest results
from SUPERCOP for Intel Haswell CPUs (long messages).

Benchmark on Intel Haswell @ 3.2 Ghz:

Before:

|  nanosecs/byte   mebibytes/sec   cycles/byte

SHAKE128 | 2.32 ns/B 411.7 MiB/s 7.41 c/B
SHAKE256 | 2.84 ns/B 336.2 MiB/s 9.08 c/B
SHA3-224 | 2.69 ns/B 354.9 MiB/s 8.60 c/B
SHA3-256 | 2.84 ns/B 336.0 MiB/s 9.08 c/B
SHA3-384 | 3.69 ns/B 258.4 MiB/s 11.81 c/B
SHA3-512 | 5.30 ns/B 179.9 MiB/s 16.97 c/B

After:

|  nanosecs/byte   mebibytes/sec   cycles/byte

SHAKE128 | 2.27 ns/B 420.6 MiB/s 7.26 c/B
SHAKE256 | 2.79 ns/B 341.4 MiB/s 8.94 c/B
SHA3-224 | 2.64 ns/B 361.7 MiB/s 8.44 c/B
SHA3-256 | 2.79 ns/B 341.5 MiB/s 8.94 c/B
SHA3-384 | 3.65 ns/B 261.4 MiB/s 11.68 c/B
SHA3-512 | 5.27 ns/B 181.0 MiB/s 16.87 c/B

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>