Fix block_perf

There's no need to have an IP address for a block throughput example/test
Fix io_page
Add the ping example

It already built without problems.
Add tcp to the Makefile
Update mirage_guest_agent to the new xenstore interface
Add the suspend example to the Makefile
Fix static_website
Update README.md
Update .gitignore
Some of the examples only build on xen: adjust Makefile to cope

We should enhance the base mirage platform so that these (or similar)
examples work.
Merge pull request #8 from djs55/more-fixes

Make more examples build