This is a library that encapsulates interaction between
a ROS Linux application and an HRT that are both running
in the same HVM.   A test application is included.

ROS/HRT interaction is done via Palacios's HVM component
and there is a detailed technical description in 
palacios/include/palacios/vmm_hvm.h.  

When the HVM is started, both the ROS (Linux) and the HRT
(for example, Nautilus) are booted simultaneously.   

A Linux application running in the ROS has control over the
HRT and the ROS..  Specifically, it can:

- reboot the HRT
- reboot the ROS
- reboot the whole HVM

- merge/unmerge its address space with the HRT's address
  space (provided the HRT can do so (e.g. Nautilus))

- asynchronously invoke functions with the HRT
  functions can be invoked on the HRT's first core 
  or simultaneously on all cores of the HRT

- synchronize with the HRT to decide on a common memory
  location to use for future, synchronous communication
  via that memory.   And teardown when this is done.

The HRT can in turn call back to the ROS application
for the following reasons, which are really only sensical
for a merged address space.  These callbacks currently include:

- system call forwarding

- page fault forwarding (for the ROS user portion of 
  the address space)

Because on the ROS side, we do everything within user
space, the ROS currently needs to poll.  It polls both 
to determine completion of a request, and get event
callbacks from the HRT.