[CIFS] CIFS support for named pipes (part 1)

This allows cifs to mount to ipc shares (IPC$)
which will allow user space applications to
layer over authenticated cifs connections
(useful for Wine and others that would want
to put DCE/RPC over CIFS or run CIFS named
pipes)

Acked-by: Rob Shearman <rob@codeweavers.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>