* lisp/files.el (write-file): Do not display confirm dialog for NS,

* lisp/files.el (write-file): Do not display confirm dialog for NS,
it does its own dialog, which can't be cancelled.

* src/nsfns.m: Remove panelOK.
(ns_fd_data): New.
(ns_run_file_dialog): New function.
(Fns_read_file_name): Fill in ns_fd_data, post an event and start the
event loop, so file dialog is popped up by ns_run_file_dialog, called
by sendEvent (Bug#14578).
(EmacsSavePanel, EmacsOpenPanel): Remove ok and cancel methods.

* src/nsterm.h (NSSavePanel): Update comment.
(NSAPP_DATA2_RUNFILEDIALOG): Define.
(ns_run_file_dialog): Declare.

* src/nsterm.m (sendEvent:): Handle NSAPP_DATA2_RUNFILEDIALOG.