Remove non Unix releated code from Unix engine.
Remove non Unix releated code from Unix engine.

Remove Symbian and VxWorks related code from Unix engine.

Change-Id: Ic5b753ef8f2f5bd41e5f465faf8425190d820f50
Reviewed-by: Denis Shienkov <1ad2dee90c89b865e4a01188e9919a005e3f77cf@yandex.ru>

RoadWorksSoftware/QtSerialPort-OS2,RoadWorksSoftware/QtSerialPort-OS2,kobolabs/qtserialport,kobolabs/qtserialport