* src/gcrypt.h.in (gcry_ctl_cmds): Add GCRYCTL_MD_CUSTOMIZE.
(gcry_md_algos): Add GCRY_MD_CSHAKE128 and GCRY_MD_CSHAKE256.
(struct gcry_cshake_customization): New.
* cipher/keccak.c (CSHAKE_DELIMITED_SUFFIX): New.
(keccak_init): Support GCRY_MD_CSHAKE128 and GCRY_MD_CSHAKE256.
(selftests_keccak): Likewise.
(cshake_input_n, cshake_input_s, _gcry_cshake_customize): New.
(cshake128_init, cshake256_init, cshake_hash_buffers): New.
(_gcry_cshake128_hash_buffers, _gcry_cshake256_hash_buffers): New.
(_gcry_digest_spec_cshake128, _gcry_digest_spec_cshake256): New.
* cipher/md.c (digest_list): Add cSHAKE md_specs.
(digest_list_algo301): Likewise.
(md_customize): New.
(_gcry_md_ctl): Support GCRYCTL_MD_CUSTOMIZE.
* src/cipher.h (_gcry_cshake_customize): New.
(_gcry_digest_spec_cshake128, _gcry_digest_spec_cshake256): New.
* src/fips.c (_gcry_fips_indicator_md): Support GCRY_MD_CSHAKE128 and
GCRY_MD_CSHAKE256.
* tests/basic.c (check_one_md): Support GCRY_MD_CSHAKE128 and
GCRY_MD_CSHAKE256 as xof.
(check_one_md_multi): Exclude GCRY_MD_CSHAKE128 and GCRY_MD_CSHAKE256
as xof.
* tests/bench-slope.c (hash_bench, kdf_bench): Exclude
GCRY_MD_CSHAKE128 and GCRY_MD_CSHAKE256.
* tests/benchmark.c (md_bench): Exclude GCRY_MD_CSHAKE128 and
GCRY_MD_CSHAKE256.