Fix compilation with zlib.
Fix compilation with zlib.

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