[werror] Fix mismatched tags (struct vs. class) inconsistence

Signed-off-by: Thorsten Behrens <tbehrens@suse.com>
On Thu, 3 Jul 2014, Thorsten Behrens wrote:
> 
> In src/include/cephfs/libcephfs.h:
> 
> >  struct ceph_dir_result;
> > -struct CephContext;
> > +class CephContext;
> 
> ah, indeed. let me update that...

FWIW I think what we really want to do is obscure the C++ CephContext type 
behind a void * typedef for this C interface.  That avoids the warning on 
that type...