Allow use of mat_fullbright through Lua.

[Isemenuk27]

Allow use of mat_fullbright through Lua. In case of using render.SuppressEngineLighting to disable map light is causing some sprites to flickering and works as combination of hooks. Having it as separate function would be nice. render.SetFullbright( boolen state ) render.GetFullbright()

[Roachdaripper]

+1

[MaslovKK]

render.SetLightingMode