Support DLBM_BACKSYSTEM as a default.
Support DLBM_BACKSYSTEM as a default.

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