pub fn sha1msg1(a: [u32; 4], b: [u32; 4]) -> [u32; 4]
sha1msg1(a, b) — the first half of the message-schedule recurrence (the XOR mixing before the rotate). dest = { W2^W0, W3^W1, W4^W2, W5^W3 } per Intel, in lane order.
sha1msg1(a, b)
dest = { W2^W0, W3^W1, W4^W2, W5^W3 }