File-name completion of non-ASCII characters on OS X (bug#22169)

File-name completion of non-ASCII characters on OS X (bug#22169)

The coding system `utf-8-nfd', locally defined in ns-win.el,
didn't provide a :pre-write-conversion method, causing file name
completion of non-ASCII characters to fail.  Solved by using the
`utf-8-hfs' coding system provided by `ucs-normalize'.

* lisp/loadup.el: Load international/ucs-normalize (when building
for ns).

* lisp/term/ns-win.el (utf-8-nfd): Made `utf-8-nfd' as alias for
`utf-8-hfs' and removed the old implementation.  Set `utf-8-hfs'
as the file name coding system.

* src/nsfns.c (ns-convert-utf8-nfd-to-nfc): Removed.