Disable non-fullscreen windows for WinRT

The integration seems to have been missing this flag. Hence we tried to
open new windows in non-fullscreen mode causing lots of issues. For
instance this resolves QCombobox popup problems.

Task-number: QTBUG-37593
Change-Id: I3d3e3699dff91dcb95613893c2a5bdefc90131b7
Reviewed-by: Andrew Knight <andrew.knight@digia.com>

src/plugins/platforms/winrt/qwinrtintegration.cpp

@@ -124,6 +124,8 @@ bool QWinRTIntegration::hasCapability(QPlatformIntegration::Capability cap) cons
     case OpenGL:
     case ApplicationState:
         return true;
+    case NonFullScreenWindows:
+        return false;
     default:
         return QPlatformIntegration::hasCapability(cap);
     }