CIFS per mount statistics

[Steve French]

Some of you all may find a recent addition to the cifs vfs interesting. 
I have added a make menuconfig option for CIFS_STATISTICS which will
write out per tree connection stats for 

	bytes read/written to that server share
	smbs sent to that server share
	successful opens, mkdirs, rmdirs, deletes to that share
	oplock breaks for files on that share
	
to /proc/fs/cifs/DebugData on the client (I may need to move this to a
different file so the proc files stay under 4k each).

This may be useful for doing quick and dirty performance tests (mounting
from the same client multiple times to different shares on the same
server each with a different filesystem or device) running tests in
parallel and comparing bytes written/read etc. stats

I added it to help more quickly tell from the client whether a
particular Samba server share was hung (we ran into a case where Samba
was blocked forever on an inode sem but so many copies of the test were
running on the client it was hard to tell what was going on on the
server) so this is a quick way to tell whether tests are progressing on
a particular Samba export.