Only use QX11Info on X11 platform
Only use QX11Info on X11 platform

Add check for Q_WS_X11 as QX11Info is not available on non X11
platforms like QPA.

RevBy: Jon Nordby

jpetersen/framework,binlaten/framework,Elleo/framework,Elleo/framework,jpetersen/framework,RHawkeyed/framework,RHawkeyed/framework