* cipher/cipher-internal.h (ocb_get_l): New.
* cipher/cipher-ocb.c (_gcry_cipher_ocb_authenticate)
(ocb_crypt): Use 'ocb_get_l' instead of '_gcry_cipher_ocb_get_l'.
* cipher/camellia-glue.c (get_l): Remove.
(_gcry_camellia_ocb_crypt, _gcry_camellia_ocb_auth): Precalculate
offset array when block count matches parallel operation size; Use
'ocb_get_l' instead of 'get_l'.
* cipher/rijndael-aesni.c (get_l): Add fast path for 75% most common
offsets.
(aesni_ocb_enc, aesni_ocb_dec, _gcry_aes_aesni_ocb_auth): Precalculate
offset array when block count matches parallel operation size.
* cipher/rijndael-ssse3-amd64.c (get_l): Add fast path for 75% most
common offsets.
* cipher/rijndael.c (_gcry_aes_ocb_crypt, _gcry_aes_ocb_auth): Use
'ocb_get_l' instead of '_gcry_cipher_ocb_get_l'.
* cipher/serpent.c (get_l): Remove.
(_gcry_serpent_ocb_crypt, _gcry_serpent_ocb_auth): Precalculate
offset array when block count matches parallel operation size; Use
'ocb_get_l' instead of 'get_l'.
* cipher/twofish.c (get_l): Remove.
(_gcry_twofish_ocb_crypt, _gcry_twofish_ocb_auth): Use 'ocb_get_l'
instead of 'get_l'.

AES            |  nanosecs/byte   mebibytes/sec   cycles/byte
       CTR enc |     0.274 ns/B    3483.9 MiB/s     0.876 c/B
       CTR dec |     0.273 ns/B    3490.0 MiB/s     0.875 c/B
       OCB enc |     0.289 ns/B    3296.1 MiB/s     0.926 c/B
       OCB dec |     0.299 ns/B    3189.9 MiB/s     0.957 c/B
      OCB auth |     0.260 ns/B    3670.0 MiB/s     0.832 c/B

AES            |  nanosecs/byte   mebibytes/sec   cycles/byte
       CTR enc |     0.273 ns/B    3489.4 MiB/s     0.875 c/B
       CTR dec |     0.273 ns/B    3487.5 MiB/s     0.875 c/B
       OCB enc |     0.248 ns/B    3852.8 MiB/s     0.792 c/B
       OCB dec |     0.261 ns/B    3659.5 MiB/s     0.834 c/B
      OCB auth |     0.227 ns/B    4205.5 MiB/s     0.726 c/B