maint: Use macros to begin/end C++ namespaces. * BaseControl.cc, BaseControl.h, ButtonControl.cc, ButtonControl.h, ButtonGroup.cc, ButtonGroup.h, Canvas.cc, Canvas.h, CheckBoxControl.cc, CheckBoxControl.h, Container.cc, Container.h, ContextMenu.cc, ContextMenu.h, EditControl.cc, EditControl.h, Figure.cc, Figure.h, FigureWindow.cc, FigureWindow.h, GLCanvas.cc, GLCanvas.h, GenericEventNotify.h, KeyMap.cc, KeyMap.h, ListBoxControl.cc, ListBoxControl.h, Logger.cc, Logger.h, Menu.cc, Menu.h, MenuContainer.h, Object.cc, Object.h, ObjectProxy.cc, ObjectProxy.h, Panel.cc, Panel.h, PopupMenuControl.cc, PopupMenuControl.h, PushButtonControl.cc, PushButtonControl.h, PushTool.cc, PushTool.h, QtHandlesUtils.cc, QtHandlesUtils.h, RadioButtonControl.cc, RadioButtonControl.h, SliderControl.cc, SliderControl.h, Table.cc, Table.h, TextControl.cc, TextControl.h, TextEdit.cc, TextEdit.h, ToggleButtonControl.cc, ToggleButtonControl.h, ToggleTool.cc, ToggleTool.h, ToolBar.cc, ToolBar.h, ToolBarButton.cc, ToolBarButton.h, annotation-dialog.cc, annotation-dialog.h, gl-select.cc, gl-select.h, qopengl-functions.h, qt-graphics-toolkit.cc, qt-graphics-toolkit.h, QTerminal.h, color-picker.cc, color-picker.h, command-widget.cc, command-widget.h, community-news.cc, community-news.h, dialog.cc, dialog.h, documentation-bookmarks.cc, documentation-bookmarks.h, documentation-dock-widget.cc, documentation-dock-widget.h, documentation.cc, documentation.h, dw-main-window.cc, dw-main-window.h, external-editor-interface.cc, external-editor-interface.h, files-dock-widget.cc, files-dock-widget.h, find-files-dialog.cc, find-files-dialog.h, find-files-model.cc, find-files-model.h, graphics-init.cc, graphics-init.h, gui-settings.cc, gui-settings.h, gui-utils.cc, gui-utils.h, history-dock-widget.cc, history-dock-widget.h, interpreter-qobject.cc, interpreter-qobject.h, led-indicator.cc, led-indicator.h, file-editor-interface.h, file-editor-tab.cc, file-editor-tab.h, file-editor.cc, file-editor.h, find-dialog.cc, find-dialog.h, marker.cc, marker.h, octave-qscintilla.cc, octave-qscintilla.h, octave-txt-lexer.cc, octave-txt-lexer.h, main-window.cc, main-window.h, news-reader.cc, news-reader.h, octave-dock-widget.cc, octave-dock-widget.h, octave-qobject.cc, octave-qobject.h, qt-application.cc, qt-application.h, qt-interpreter-events.cc, qt-interpreter-events.h, qt-utils.h, release-notes.cc, release-notes.h, resource-manager.cc, resource-manager.h, set-path-dialog.cc, set-path-dialog.h, set-path-model.cc, set-path-model.h, settings-dialog.cc, settings-dialog.h, shortcut-manager.cc, shortcut-manager.h, tab-bar.cc, tab-bar.h, terminal-dock-widget.cc, terminal-dock-widget.h, variable-editor-model.cc, variable-editor-model.h, variable-editor.cc, variable-editor.h, welcome-wizard.cc, welcome-wizard.h, workspace-model.cc, workspace-model.h, workspace-view.cc, workspace-view.h: Use new macros to begin/end C++ namespaces.

########################################################################
##
## Copyright (C) 2006-2022 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## 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
## <https://www.gnu.org/licenses/>.
##
########################################################################

%!shared x, a, b
%! x = [1,2];
%! a = 1;
%! b = 2;

%!test
%! y = [a... # comments here ok
%! b];
%! assert (y, x);

## FIXME: Next 3 tests use '\' continuation outside of a double-quoted string
##        This behavior is deprecated and will be removed at some point.
##        When it does these
%!test
%! x = [1;2];
%! y = [a... # comments here ok
%! ;\
%!
%! b];
%! assert (y, x);

%!assert (1 + ...
%! 2 - \# comments here ok
%! 3 / ... # comments here ok
%! -1,6);

%!function y = f (a,...
%!                b,  ...
%!                c,  ...   % comments ok
%!                x,  # continuation characters not required in parens
%!                y,  \# but they should work too.
%!                z)
%!
%!  y = 1;
%!endfunction
%!
%!assert (f (), 1)

## String continuation using '\'
%!assert (["abc\
%! def"], "abc def")

%!test
%!assert (1 == 1
%! && 2 == 2
%! || 3 == 5);

%!test
%! x = [1, ...
%!
%! ...
%!
%! 2];
%! y = [1;2];
%! assert (y, x);

%!test
%! x = [1 ,...
%! 2];
%! y = [1,2];
%! assert (y, x);

%!test
%! x = [ 1 , ...
%! 2];
%! y = [1,2];
%! assert  (y, x);

%!test
%! x = [ 1 , ...anything after the ... is ignored
%! 2];
%! y = [1,2];
%! assert  (y, x);