<sys/bio.h>.
<sys/bio.h> is now a prerequisite for <sys/buf.h> but it shall
not be made a nested include according to bdes teachings on the
subject of nested includes.
Diskdrivers and similar stuff below specfs::strategy() should no
longer need to include <sys/buf.> unless they need caching of data.
Still a few bogus uses of struct buf to track down.
Repocopy by: peter
data and sense information for target mode devices for which no other
peripheral driver is attached. This simplifies the task of dealing with
luns that are not otherwise enabled for target mode if the controller
does not have firmware that automatically deals with this case (e.g.
the aic7xxx driver).
