More abstraction of file system data types, to move to a 64

More abstraction of file system data types, to move to a 64
bit file interface for the NT SMB's.

Created a new define, SMB_STRUCT_STAT that currently is
defined to be struct stat - this wil change to a user
defined type containing 64 bit info when the correct
wrappers are written for 64 bit stat(), fstat() and lstat()
calls.

Also changed all sys_xxxx() calls that were previously just
wrappers to the same call prefixed by a dos_to_unix() call
into dos_xxxx() calls. This makes it explicit when a pathname
translation is being done, and when it is not.

Now, all sys_xxx() calls are meant to be wrappers to mask
OS differences, and not silently converting filenames on
the fly.

Jeremy.