Function indy_sys::anoncreds::indy_prover_create_credential_req

#[no_mangle]
pub unsafe extern "C" fn indy_prover_create_credential_req(
    command_handle: CommandHandle, 
    wallet_handle: WalletHandle, 
    prover_did: CString, 
    cred_offer_json: CString, 
    cred_def_json: CString, 
    master_secret_id: CString, 
    cb: Option<ResponseStringStringCB>
) -> Error