cipher: Support random-override with PUBKEY_FLAG_BYTE_STRING.
* cipher/pubkey-util.c (_gcry_pk_util_init_encoding_ctx): Initialize RND and RNDLEN field. (_gcry_pk_util_free_encoding_ctx): Release memory by RND field. (_gcry_pk_util_data_to_mpi): Support optional "random-override". * src/cipher.h (struct pk_encoding_ctx): Add RND and RNDLEN.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>