Core: Fix surface.h include in core_strings.h using core/
Core: Fix surface.h include in core_strings.h using core/

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