improve encapsulation of history window object * history-dockwidget.h, history-dockwidget.cc (history_dock_widget::history_dock_widget): Set status tip here. Connect history_dock_widget::information signal to main_window::report_status_message. Connect history_dock_widget::command_double_clicked signal to main_window::handle_command_double_clicked. (history_dock_widget::connect_visibility_changed, history_dock_widget::focus, history_dock_widget::handle_visibility): New functions. * main-window.h, main-window.cc (main_window::history_window): Rename from _history_dock_widget. Don't use a pointer. Change all uses. (main_window::main_window): Initialize it here. (main_window::~main_window): Don't delete _history_dock_widget. (main_window::focus_history_window_signal): New signal. (main_window::focus_history_window): Rename from main_window::focus_command_history. Emit focus_history_window_signal instead of performing actions here. (main_window::handle_command_history_visible): Delete. (main_window::connect_visibility_changed): Call history_window.connect_visibility_changed instead of performing actions here. (main_window::construct): Don't create _history_dock_widget. Adapt signal/slot connections for new history_window object.

## Copyright (C) 2004-2012 John W. Eaton
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or (at
## your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} isunix ()
## Return true if Octave is running on a Unix-like system and false otherwise.
## @seealso{ismac, ispc}
## @end deftypefn

function retval = isunix ()

  if (nargin == 0)
    retval = octave_config_info ("unix");
  else
    print_usage ();
  endif

endfunction


%!assert (islogical (isunix ()))

%!error isunix (1)