libdirect: add note about debug macro optimisation (domain check prior to parameter passing)
libdirect: add note about debug macro optimisation (domain check prior to parameter passing)

Signed-off-by: Denis Oliver Kropp <3fa78fd63dd76ba74a102cf4e1e79303ef9149a1@directfb.org>

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