Fix stale email addresses in xenstat and xentop.

Fix stale email addresses in xenstat and xentop.

Our @us.ibm.com emails cannot forward to us; we do not have access to
them when not interning at IBM.  People have attempted to reach us via
those addresses and failed; occasionally they've Googled for a current
address, which made us realize the problem.  Change each email to a
more permanent address, so people can reach us in the future.  Change
bug reporting addresses to a xen mailing list rather than an
individual.

Signed-off-by: Josh Triplett <josh@kernel.org>