Obsolete the QSerialPort::Unknown* enumeration values

It has no use case, so we should get rid of this API in the future. We can deprecate it for now. It has been added mistakenly. It is the exposure of weird windows API going againt the serial port "standard" behavior.

This has been misunderstood before, so let us clean it up while giving a warning for weird API options with Windows, Unix and Symbian.

Here is the relevant MSDN docs where we treated fParity weirdly:

http://msdn.microsoft.com/en-us/library/windows/desktop/aa363214%28v=vs.85%29.aspx

The rest is similarly. Changes to follow:

https://codereview.qt-project.org/72795

and

https://codereview.qt-project.org/72925