Add hello_world1.

This example attempts to verify that Accelio permits
applications to relibly free resources it has allocated and
presented to libxio.

This code appears to have bounded memory utilization after
startup, and demonstrates how to reclaim memory for completed
requests.

I think it's unfortunate that msg->request (on_msg callback)
points to memory, rather than (say) 0.  Should be better
documented.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>