COMP: Q_OS_X11 doesn't exist with Qt4 replacing it back to Q_WS_X11

Change-Id: I39967a78f56a26c1c33beeb46df3d8c5ace5cc37
Merge topic 'Fix-Qt5-Support' into master

b11d523e COMP: Q_OS_X11 doesn't exist with Qt4 replacing it back to Q_WS_X11