s3: Change SMB_VFS_OPEN to take an smb_filename struct

s3: Change SMB_VFS_OPEN to take an smb_filename struct

This was a little messy because of all of the vfs modules I had to
touch.  Most of them were pretty straight forward, but the streams
modules required a little attention to handle smb_filename.  Since the
use of smb_filename enables the vfs modules to access the raw,
over-the-wire stream, a little bit of the handling that was being done
by split_ntfs_stream_name has now been shifted into the individual
stream modules.  It may be a little more code, but overall it gives
more flexibility to the streams modules, while also allowing correct
stream handling.