Peter M. Groen / libmodbus

- 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

bit is used HIGH to able to transmit, or LOW.

https://bugzilla.redhat.com/show_bug.cgi?id=724942

Bonus side effect: the integer isn't present anymore when TIOCSRS485
isn't supported on non Win32 platforms.

When there's no RS485 support available (e.g. on Win32), the modbus_rtu_t
data structure does not have the serial_mode member. It therefore must
not be used in modbus_rtu_get_serial_mode() if HAVE_DECL_TIOCSRS485 is
not defined. Fixes Win32 build with recent versions of libmodbus.

The ENOTSUP error code is not defined on Win32. However we can simply
use an equivalent from the Windows Socket API (WSA). Fixes Win32 build
with recent versions of libmodbus.

Patch provided by Ivo De Decker <Ivo.DeDecker@UGent.be>.
Debian library packaging guide states "The package name should match the
shared library SONAME"
(http://www.netfort.gr.jp/~dancer/column/libpkg-guide/libpkg-guide.html)

Patch provided by Ivo De Decker <Ivo.DeDecker@UGent.be>

http://wiki.debian.org/ReleaseGoals/LAFileRemoval

Add macros in libmodbus.txt and:
- modbus_get_byte_from_bits.txt
- modbus_get_float.txt
- modbus_reply.txt
- modbus_reply_exception.txt
- modbus_set_bits_from_byte.txt
- modbus_set_bits_from_bytes.txt
- modbus_set_float.txt

The function name was confusing because the write operation is performed
before the read. Take care to swap the arguments in the migration process.

Avoid incompatibility with GPLv2 program. This change has been approved by
Tobias Doerffel, Florian octo Forster and Hannu Vuolasaho.

Thank you Ivo De Decker.