Peter M. Groen / libmodbus

- new functions modbus_slave_init_listen_tcp, modbus_slave_accept_tcp,
  modbus_slave_slave_receive.
- removed printf in modbus.c: 'Connection closed'
- new slave test, bandwith-slave-many-up
- updated build scripts
- updated MIGRATION document file

- use strerror instead of error number

Thanks to Justin Carroll to have reported and tested my patch.

Invalid error check in modbus_init_listen_tcp

- Add many comments to receive_msg and modbus_receive functions.
- The use of response_length for good response was confusing.

- Return test on read and recv slightly more robust
- Fix a comment

- code is easier to understand
- code is bit faster.

This new value isn't appropriate for a serial link.

- reduce the number of variables to store return values (status,
  query_ret and response_ret -> ret)
- add some comments

modbus_check_response() crashes on an invalid exception code

- Update the NEWS file

- Add test files to examples directory in libmodbus-dev.
- Add MIGRATION file to libmodbus-dev.
- Define the compatibility level to 6.
- Add MIGRATION to EXTRA_DIST in Makefile.am
- Add README to  EXTRA_DIST in tests/Makefile.am
- Add unit-test.h as dependency in tests/Makefile.am

The test is now outside of check_crc16 and directly included in
receive_msg().

- The coil and registers are wrote by the master and not assigned by the
  slave anymore
- The data used to write are the ones in unit-test.h
- The read test is done after the write test