Added CubeMapTexture::setSeamless().
Added CubeMapTexture::setSeamless().

ashimidashajia/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,ashimidashajia/magnum,DerThorsten/magnum,ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum,ashimidashajia/magnum