Peter M. Groen / libmodbus

Fix EXXX values defined in Microsoft C Runtime 10

Thanks to Carlos Tangerino

Thanks to oldfaber

Thanks to oldfaber.

Original patch provided by Michael Haberler <git@mah.priv.at>.

Thanks to Stefan Finzel for the bug report

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

Thanks to Thomas Stalder and Torello Querci for the report.

Original patch for new connect function by Thomas Stalder.

Thanks to Bernhard Agthe.

- export new symbols to create specific behavior (RTU)
- the flag can't only be set by slaves
- new tests

Warning, modbus_receive returns 0 when a query is ignored.

- function removed from TCP and RTU code and from backend structure
- updated documentation
- updated examples

- remove static variable in the library

libabc is a really good source of inspiration!
https://git.kernel.org/?p=linux/kernel/git/kay/libabc.git

The serial mode and rts flags are now initialized in new function.
Original patch provided by Jaime Alberto Silva
<jaime@sgautomatizacion.com>.

- new function _modbus_rtu_pre_check_confirmation
- new special test value to trigger an invalid response
- add unit test to cover invalid TID too

Thanks to Andrea Mattia

Original patch provided by Thomas Stalder.

Thanks to Pavel Mazniker for the report.

- avoid export of _modbus_rtu_set_rts and change its name to avoid
  confusion
- namespace RTU functions and constants
- use_rts is renamed rts
- add missing '_' in function name
- remove useless debug message in usual write
- wrong message about 'not supported'
- add check for TIOCM_RTS support
- block RTS flow control when not available