Undocumented in source but is binding to an external library. You might be able to learn more by searching the web for its name.
intgnutls_privkey_import_rsa_raw(gnutls_privkey_t key, const(gnutls_datum_t)* m, const(gnutls_datum_t)* e, const(gnutls_datum_t)* d, const(gnutls_datum_t)* p, const(gnutls_datum_t)* q, const(gnutls_datum_t)* u, const(gnutls_datum_t)* e1, const(gnutls_datum_t)* e2)