do not return non-visible clients for e_client_under_pointer_get()
do not return non-visible clients for e_client_under_pointer_get()

a hidden client should not be considered "under the mouse" since its
geometry is undefined until it becomes visible again

fix T1069

tizenorg/platform.upstream.enlightenment,tasn/enlightenment,rvandegrift/e,tasn/enlightenment,tasn/enlightenment,tizenorg/platform.upstream.enlightenment,rvandegrift/e,tizenorg/platform.upstream.enlightenment,rvandegrift/e