[PATCH] Change "xor" name in cpu_core to allow building with iso646.h or C++ compiler

[Simon Marchi]

CCing Mike so he knows there is a sim patch.

The patch has wrapped lines,  which makes it difficult to apply.  Since it is small
I was able to fix it up by hand, but for the future I suggest you look into using
git-send-email, which avoids these problems.

The patch looks obvious enough to me and I built-tested it, so I took the liberty
of pushing it.

Thanks!

Simon