Peter M. Groen / libmodbus

- 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

- rename test-master-random => random-test-master
- fix memset
- update README
- add the files to configure.ac and wscript

I don't know how to manage many versions.

- s/datas/data/
- the warning is now an error
- add some checks in modbus.c
- add unit tests
- remove the TODO item
- minor 80 columns changes