Safer modbus_close
New functions to set/get swapped floats (LSB)
Documentation of new modbus_[get|set]_float_swapped functions
Documentation improvements to libmodbus page
Missing UT_IREAL_SWAPPED
Rename modbus_set_float_swapped to modbus_set_float_dcba
Baud rate until 4,000,000 (POSIX), 1,000,000 (Windows) (closes #93)
Avoid a level of imbrication in bandwidth-server-many-up
Sleep for delay of response timeout before reconnect (closes #77)

Thanks to Karl Palsson.
Protect all public functions against invalid context

- change return argument from void to int
- update documentation
Always set socket to -1 on close()
Returns -1 on invalid mode in modbus_rtu_set_rts
Improve socket init and close in tests
Update NEWS file
Remove (not so useful) ld options not supported on Mac OS X
Portable use of bswap_32
Try to fix MinGW compilation (EXTERN to nop)

This regression comes from Visual Studio patches.
Avoid overriding of bswap_32 because bswap_16 is undefined
Avoid to shadow 'boolean' on weird platform (Windows)
Avoid empty  _modbus_rtu_ioctl_rts when no HAVE_DECL_TIOCM_RTS