[MERGE] Report the number of VFS calls in -Dhpss output

[Andrew Bennetts]

Jonathan Lange wrote:
> Hello,
> 
> As discussed in an earlier thread, this patch extends the smart
> server's _DebugCounter to maintain a separate count of VFS calls.
> 
> It does this by inspecting the 'method' attribute of params, fetching
> the request object from the registry and checking to see whether it's
> a subclass of VfsRequest.
> 
> I've updated the NEWS file, but didn't write any tests, since I
> couldn't find any for the existing functionality. I did double check
> the count against the .bzr.log though, and the numbers work out just
> fine.

Looks good to me.

bb:approve

-Andrew.