RSA renaming. Updated all callers.

* rsa-sign.c (rsa_private_key_init, rsa_private_key_clear)
(rsa_private_key_prepare): Renamed functions.
* rsa.c (rsa_public_key_init, rsa_public_key_clear)
(rsa_public_key_prepare): Renamed functions.

Rev: src/nettle/ChangeLog:1.167
Rev: src/nettle/examples/rsa-keygen.c:1.8
Rev: src/nettle/examples/rsa-sign.c:1.4
Rev: src/nettle/examples/rsa-verify.c:1.3
Rev: src/nettle/rsa-compat.c:1.7
Rev: src/nettle/sexp2rsa.c:1.10
Rev: src/nettle/testsuite/rsa-keygen-test.c:1.5
Rev: src/nettle/testsuite/rsa-test.c:1.6
Rev: src/nettle/testsuite/rsa2sexp-test.c:1.5
Rev: src/nettle/testsuite/sexp2rsa-test.c:1.6