zile: display minibuf errors correctly in batch mode.

* lib/zile/minibuf.lua (minibuf_refresh): In batch mode, still
pass the minibuf contents to term_minibuf_write, even though
there is no cur_wp.
* lib/zmacs/main.lua (process_args): Don't try to display in
the minibuf area before we know whether we'll be in batch mode
at the end of arguments.  Instead pass back any error message
to the caller.
(main): Action error message from process_args once
term_minibuf_write knows whether there is a window to display
in or not.
* lib/zz/zz.lua (process_args, main): And again!

Signed-off-by: Gary V. Vaughan <gary@gnu.org>