Add RSA-OAEP encryption/decryption to Nettle

Hello,

I've made a new Merge Request in the nettle gitlab repo to provide RSA-OAEP encryption and decryption: https://git.lysator.liu.se/nettle/nettle/-/merge_requests/20

It adds 2 new functions:

int pkcs1_oaep_encrypt (size_t key_size, void *random_ctx, nettle_random_func *random, size_t hlen, size_t label_length, const uint8_t *label, size_t message_length, const uint8_t *message, mpz_t m);

int pkcs1_oaep_decrypt (size_t key_size, const mpz_t m, size_t hlen, size_t label_length, const uint8_t *label, size_t *length, uint8_t *message);

The parameter hlen is the output length of the SHA function used for masking data: - SHA1_DIGEST_SIZE - SHA256_DIGEST_SIZE - SHA384_DIGEST_SIZE - SHA512_DIGEST_SIZE

Is it possible to get feedback for this MR and eventually push it to the master branch?

Thanks in advance

/Nicolas