Added dfb_surface_data_offset() which calculates the data pointer for a given coordinate (x/y) based on the pointer and pitch passed to it.
Added dfb_surface_data_offset() which calculates the data pointer for a
given coordinate (x/y) based on the pointer and pitch passed to it.

It also handles DSCAPS_SEPARATED depending on the surface which is passed, too.

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