Fixed compilation error caused by wl_xcomposite

It seems like wl_xcomposite was renamed to qt_xcomposite, but not in all places, what cased compilation error, so all remaining appearences where renamed.

Change-Id: I2850dfb428ea39e9a30ec076500c1e26ce1fe5da
Reviewed-by: Jan Arne Petersen <jan.petersen@kdab.com>
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>