mapnik.go
func (m *Map) SetBufferSize(s int) {
	C.mapnik_map_set_buffer_size(m.m, C.int(s))
}
func (m *Map) SetBufferSize(s int) {
	C.mapnik_map_set_buffer_size(m.m, C.int(s))
}
// SetBufferSize sets the pixel buffer at the map image edges where Mapnik should not render any labels.