* cipher/kdf.c (argon2_ctl): Remove.
(argon2_iterator): Remove.
(argon2_compute_segment): Change the API.
(argon2_compute): New.
(argon2_open): No optional N_THERADS any more.
(_gcry_kdf_ctl): Remove.
(_gcry_kdf_iterator, _gcry_kdf_compute_segment): Remove.
(_gcry_kdf_compute): New.
* src/gcrypt-int.h: Update declarations.
* src/gcrypt.h.in: Likewise.
* src/libgcrypt.def: Update.
* src/libgcrypt.vers: Update.
* src/visibility.c: Update.
* src/visibility.h: Update.
* tests/t-kdf.c (check_argon2): Update the test with change of new
API.