Added a dfb_thread_testcancel().
Added a dfb_thread_testcancel().

sklnet/DirectFB,sklnet/DirectFB,kaostao/directfb,lancebaiyouview/DirectFB,deniskropp/DirectFB,DirectFB/directfb,kevleyski/DirectFB-1,Distrotech/DirectFB,kevleyski/directfb,kevleyski/DirectFB-1,kevleyski/directfb,jcdubois/DirectFB,djbclark/directfb-core-DirectFB,deniskropp/DirectFB,kaostao/directfb,deniskropp/DirectFB,kaostao/directfb,djbclark/directfb-core-DirectFB,DirectFB/directfb,mtsekm/test,sklnet/DirectFB,djbclark/directfb-core-DirectFB,sklnet/DirectFB,dfbdok/DirectFB1,DirectFB/directfb,lancebaiyouview/DirectFB,mtsekm/test,dfbdok/DirectFB1,deniskropp/DirectFB,Distrotech/DirectFB,kevleyski/directfb,lancebaiyouview/DirectFB,Distrotech/DirectFB,mtsekm/test,lancebaiyouview/DirectFB,jcdubois/DirectFB,kevleyski/DirectFB-1,kevleyski/directfb,jcdubois/DirectFB,kevleyski/DirectFB-1,dfbdok/DirectFB1,djbclark/directfb-core-DirectFB