* cipher/cipher.c (cipher_setkey): Pass cipher object pointer to
cipher's setkey function.
* cipher/arcfour.c: Add gcry_cipher_hd_t parameter for setkey
functions and update selftests to pass NULL pointer.
* cipher/blowfish.c: Ditto.
* cipher/camellia-glue.c: Ditto.
* cipher/cast5.c: Ditto.
* cipher/chacha20.c: Ditto.
* cipher/cipher-selftest.c: Ditto.
* cipher/des.c: Ditto.
* cipher/gost28147.c: Ditto.
* cipher/idea.c: Ditto.
* cipher/rfc2268.c: Ditto.
* cipher/rijndael.c: Ditto.
* cipher/salsa20.c: Ditto.
* cipher/seed.c: Ditto.
* cipher/serpent.c: Ditto.
* cipher/twofish.c: Ditto.
* src/cipher-proto.h: Ditto.