include: Add DFBSurfaceFlipFlags to directfb_strings.h
include: Add DFBSurfaceFlipFlags to directfb_strings.h

Signed-off-by: dok <3fa78fd63dd76ba74a102cf4e1e79303ef9149a1@directfb.org>

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