QSerialPort::open() useless warning in windows

There's warning that can't be avoided and it's probably useless. It comes allways when opening port. Can be reproduced for example QtSerialPort manual test.

void __thiscall QSerialPortPrivate::detectDefaultSettings(void): Unexpected flow control settings

It's caused because flowcontrol is not initialized when opening port. And it can't be done before open.

Suggestion is to initialize it in QSerialPortPrivate::open() like other settings:

   currentDcb.fRtsControl = RTS_CONTROL_DISABLE;