sl_compress_init
void sl_compress_init(struct slcompress *, int);
sl_compress_init(&priv->slc, c->maxChannel);
sl_compress_init(&ipcp->vj.cslc, ipcp->cfg.vj.slots - 1);
sl_compress_init(&ipcp->vj.cslc, (ipcp->peer_compproto >> 8) & 255);
extern void sl_compress_init(struct slcompress *, int);