mgx_bitblt
static void mgx_bitblt(void *, int, int, int, int, int, int, int);
sc->sc_gc.gc_bitblt = mgx_bitblt;
mgx_bitblt(sc, x, y, x, y, wi, he, ROP_INV);
mgx_bitblt(sc, x, y, x, y, wi, he, ROP_INV);
mgx_bitblt(sc, xs, y, xd, y, width, height, ROP_SRC);
mgx_bitblt(sc, x, ys, x, yd, width, height, ROP_SRC);