Mention the multi-image functionality in the usage string.
Mention the multi-image functionality in the usage string.

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