enc_quarterround
u32 w0 = enc_quarterround(w, 0, *rkp++);
u32 w1 = enc_quarterround(w, 1, *rkp++);
u32 w2 = enc_quarterround(w, 2, *rkp++);
u32 w3 = enc_quarterround(w, 3, *rkp++);