bench-slope: add KDF/PBKDF2 benchmark

* tests/bench-slope.c (bench_kdf_mode, bench_kdf_init, bench_kdf_free)
(bench_kdf_do_bench, kdf_ops, kdf_bench_one, kdf_bench): New.
(print_help): Add 'kdf'.
(main): Add KDF benchmarks.

Introduce KDF benchmarking to bench-slope. Output is given as
nanosecs/iter (and cycles/iter if --cpu-mhz used). Only PBKDF2
is support with this initial patch.

For example, below shows output of KDF bench-slope before
and after commit "md: keep contexts for HMAC in GcryDigestEntry",
on Intel Core i5-4570 @ 3.2 Ghz:

Before:

$ tests/bench-slope --cpu-mhz 3201 kdf
KDF:

|  nanosecs/iter   cycles/iter

PBKDF2-HMAC-MD5 | 882.4 2824.7
PBKDF2-HMAC-SHA1 | 832.6 2665.0
PBKDF2-HMAC-RIPEMD160 | 1148.3 3675.6
PBKDF2-HMAC-TIGER192 | 1339.6 4288.2
PBKDF2-HMAC-SHA256 | 1460.5 4675.1
PBKDF2-HMAC-SHA384 | 1723.2 5515.8
PBKDF2-HMAC-SHA512 | 1729.1 5534.7
PBKDF2-HMAC-SHA224 | 1424.0 4558.3
PBKDF2-HMAC-WHIRLPOOL | 2459.7 7873.5
PBKDF2-HMAC-TIGER | 1350.2 4322.1
PBKDF2-HMAC-TIGER2 | 1348.7 4317.3
PBKDF2-HMAC-GOSTR3411_94 | 7374.1 23604.4
PBKDF2-HMAC-STRIBOG256 | 6060.0 19398.1
PBKDF2-HMAC-STRIBOG512 | 7512.8 24048.3
PBKDF2-HMAC-GOSTR3411_CP | 7378.3 23618.0
PBKDF2-HMAC-SHA3-224 | 2789.6 8929.5
PBKDF2-HMAC-SHA3-256 | 2785.1 8915.0
PBKDF2-HMAC-SHA3-384 | 2955.5 9460.5
PBKDF2-HMAC-SHA3-512 | 2859.7 9153.9

=

After:

$ tests/bench-slope --cpu-mhz 3201 kdf
KDF:

|  nanosecs/iter   cycles/iter

PBKDF2-HMAC-MD5 | 405.9 1299.2
PBKDF2-HMAC-SHA1 | 392.1 1255.0
PBKDF2-HMAC-RIPEMD160 | 540.9 1731.5
PBKDF2-HMAC-TIGER192 | 637.1 2039.4
PBKDF2-HMAC-SHA256 | 691.8 2214.3
PBKDF2-HMAC-SHA384 | 848.0 2714.3
PBKDF2-HMAC-SHA512 | 875.7 2803.1
PBKDF2-HMAC-SHA224 | 689.2 2206.0
PBKDF2-HMAC-WHIRLPOOL | 1535.6 4915.5
PBKDF2-HMAC-TIGER | 636.3 2036.7
PBKDF2-HMAC-TIGER2 | 636.6 2037.7
PBKDF2-HMAC-GOSTR3411_94 | 5311.5 17002.2
PBKDF2-HMAC-STRIBOG256 | 4308.0 13790.0
PBKDF2-HMAC-STRIBOG512 | 5767.4 18461.4
PBKDF2-HMAC-GOSTR3411_CP | 5309.4 16995.4
PBKDF2-HMAC-SHA3-224 | 1333.1 4267.2
PBKDF2-HMAC-SHA3-256 | 1327.8 4250.4
PBKDF2-HMAC-SHA3-384 | 1392.8 4458.3
PBKDF2-HMAC-SHA3-512 | 1428.5 4572.7

=

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