BOOST_ASIO_DISABLE_SERIAL_PORT doesn't work as expected

[anonymous]

The expected result is that none of the serial port code would be included. This does not happen, many of the serial port related headers get included and potentially cause many compile errors (for example, if your platform doesn't have termios).

Obviously there are a number of different ways to handle this problem, I can provide a patch if you like, but placement of the checks is just a matter of opinion (it seems like one would want to just put the check in the top level serial port files after boost/config.hpp is included, however).