Updated doc to address comments.  Many changes are typos, but
some are more more substantive.

								JJ


Version title is a hyperlink the versioning section
Rewrote concurrency section to be less concurrent
Removed disconnection recovery section - disconnect now causes client device reset
Message type is now enumerated in flags to distinguish it from message attributes
argsz fields use VFIO definitions instead of being reserved
sys/vfio.h -> linux/vfio.h