X11: fix window placement on multi-monitor setups

This reverts 6e7bc91d28c232676ae41abf4d819e598c019bdd and follows direction given by Chris Wilson at freedesktop: https://bugs.freedesktop.org/show_bug.cgi?id=82619

Window managers may have the policy to place the window where the mouse is. Hence we need to call XWarpPointer before XMapRaised.