message: [client] restore accidentally deleted header
  This was added by but accidentally removed by
  Closes:
  Approved by: sunmilee
diff: @@ -113,6 +113,24 @@ struct LibraEvent {
  */
  enum LibraStatus libra_LibraAccountResource_from(const uint8_t *buf, size_t len, struct LibraAccountResource *out);
  +/*!
  + * Get serialized signed transaction from a list of transaction parameters
  + *
  + * To get the serialized transaction in a memory safe manner, the client needs to pass in a pointer to a pointer to the allocated memory in rust
  + * and call free on the memory address with `libra_free_bytes_buffer`.
  + * @param[in] sender_private_key is sender's private key
  + * @param[in] sequence is the sequence number of this transaction corresponding to sender's account.
  + * @param[in] max_gas_amount is the maximal total gas specified by wallet to spend for this transaction.
  + * @param[in] gas_unit_price is the maximal price can be paid per gas.
  + * @param[in] gas_identifier is the identifier of the coin to be used as gas.
  + * @param[in] expiration_time_secs is the time this TX remain valid, the format is unix timestamp.
  + * @param[in] script_bytes is the script bytes for given transaction.
  + * @param[in] script_len is the length of script_bytes array.
  + * @param[out] ptr_buf is the pointer that will be filled with the memory address of the transaction allocated in rust. User takes ownership of pointer returned by *buf, which needs to be freed using libra_free_bytes_buffer
  + * @param[out] ptr_len is the length of the signed transaction memory buffer.
  +*/
  +enum LibraStatus libra_SignedTransactionBytes_from(const uint8_t sender_private_key[LIBRA_PRIVKEY_SIZE], uint64_t sequence, uint64_t max_gas_amount, uint64_t gas_unit_price, const char* gas_identifier, uint64_t expiration_time_secs, const uint8_t *script_bytes, size_t script_len, uint8_t **ptr_buf, size_t *ptr_len);
  +
  /*!
  * Get script bytes for a P2P transaction
  *
  