func XORBytes(dst, a, b []byte) int {
	n := len(a)
	if len(b) < n {
		n = len(b)
	}
	if n == 0 {
		return 0
	}
	_ = dst[n-1]
	xorBytesVSX(&dst[0], &a[0], &b[0], n)
	return n
}
XORBytes xors the bytes in a and b. The destination should have enough space, otherwise xorBytes will panic.
Returns the number of bytes xor'd.
package byteutils