Function indy_sys::ledger::indy_build_get_txn_request

#[no_mangle]
pub unsafe extern "C" fn indy_build_get_txn_request(
    command_handle: CommandHandle, 
    submitter_did: CString, 
    ledger_type: CString, 
    seq_no: i32, 
    cb: Option<ResponseStringCB>
) -> Error