Peter M. Groen / libmodbus

- more coherent
- namespace
- opaque and smaller context
- usual wording

A new API will be committed to remove the slave in TCP communication.

The ID used at init time will be the device ID of the caller and
the server ID in request functions is the target to reach.

This reverts commit df0cf7927249954f15e0aa85b02d21b990fa9af9.
Use <modbus.h> in tests.

- returns -1 on error and set errno
- error recovery system was flawed
- error recovery disabled by default
- remove a malloc

This time the change is definitive :)

- the return value is used to pass the message length
- remove the hack on exception check in modbus receive
- update tests

- adjusts various comments on return values
- updated tests
- added entry to MIGRATION

- MAJOR changes to the API (see MIGRATION)
- New unit tests
- Removed TODO list
- Updated NEWS & MIGRATION files

This change improves the conformance with the PDU and ADU definitions of the
Modbus protocol and reduces the number of additions.

- upgrade to WAF 1.5.3
- smaller WAF scripts
- fix using of modbus.h with WAF
- updated configure.ac and Makefile.am files
- change include paths in test files

- 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

- 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

- Reduce the max message length to 256 (PI_M300)
- s/size/length/

- use uint8_t* for the query

- Major changes to unit-test-master/slave to add 4 tests
- Use new functions to manipulate bits
- Reduce memory usage (allocate only the required space and use
  uint[8|16]_t pointers)

- Separate unit-test-master and test-master-random