Windows: refactor fs acl funcs into fs_acl.c

Windows: refactor fs acl funcs into fs_acl.c

The ACL structure definitions and manipulation functions
were defined both in WINNT/afsd/fs.c and WINNT/client_exp/gui2fs.cpp.
Extract them to WINNT/afsd/fs_acl.c and refactor them so that a
single copy can be maintained for both modules.

The most significant change is to CleanAcl() which now accepts
a cellname instead of a file path.  By accepting a cellname the
ACL functionality is completely isolated from the path processing
and pioctl operations.

At the present time, fs.exe calls CleanAcl() with a cell name
and afs_shl_ext.dll does not.  All callers in fs.c have been updated
to use the new behavior.

gui2fs.cpp also comments functions that exist in the file but
have no caller.  These can be removed at a later date if they
are not required.

Change-Id: Ibc5f411c6410769bdfeaf9e37b6d39a64958baff
Reviewed-on: http://gerrit.openafs.org/4783
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>