Fix bug #7410 - samba sends "raw" inode number as uniqueid with unix extensions.

Fix  bug #7410 - samba sends "raw" inode number as uniqueid with unix extensions.

Move to a consistent get_FileIndex() function for all inode returns,
that checks if st_dev on the file is identical to the top directory
dev_t of the exported share, and if so uses the raw 64-bit inode
number. If it isn't (we've traversed a mount point) - return what
we used to do for Windows which is the concatination of the bottom
32-bits of the inode with the 32-bit device number. We can get more
creative with this over time (hashing?) if we want as now all inode returns go
through this single function.

Jeremy.