vendor: Move back to upstream KCP (fixes #4407)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4614

vendor/github.com/klauspost/reedsolomon/galois_arm64.go

@@ -0,0 +1,48 @@
+//+build !noasm
+//+build !appengine
+
+// Copyright 2015, Klaus Post, see LICENSE for details.
+// Copyright 2017, Minio, Inc.
+
+package reedsolomon
+
+//go:noescape
+func galMulNEON(c uint64, in, out []byte)
+
+//go:noescape
+func galMulXorNEON(c uint64, in, out []byte)
+
+func galMulSlice(c byte, in, out []byte, ssse3, avx2 bool) {
+	var done int
+	galMulNEON(uint64(c), in, out)
+	done = (len(in) >> 5) << 5
+
+	remain := len(in) - done
+	if remain > 0 {
+		mt := mulTable[c]
+		for i := done; i < len(in); i++ {
+			out[i] = mt[in[i]]
+		}
+	}
+}
+
+func galMulSliceXor(c byte, in, out []byte, ssse3, avx2 bool) {
+	var done int
+	galMulXorNEON(uint64(c), in, out)
+	done = (len(in) >> 5) << 5
+
+	remain := len(in) - done
+	if remain > 0 {
+		mt := mulTable[c]
+		for i := done; i < len(in); i++ {
+			out[i] ^= mt[in[i]]
+		}
+	}
+}
+
+// slice galois add
+func sliceXor(in, out []byte, sse2 bool) {
+	for n, input := range in {
+		out[n] ^= input
+	}
+}