maint: style check C++ files in src/ and libgui/ ahead of 7.1 release. * ButtonGroup.cc, Canvas.cc, CheckBoxControl.cc, Container.cc, ContextMenu.cc, EditControl.cc, Figure.cc, Figure.h, FigureWindow.cc, GenericEventNotify.h, ListBoxControl.cc, ListBoxControl.h, Logger.cc, Menu.cc, Object.cc, Panel.cc, PopupMenuControl.cc, PushButtonControl.cc, PushTool.cc, RadioButtonControl.cc, SliderControl.cc, Table.cc, Table.h, TextControl.cc, ToggleButtonControl.cc, ToggleTool.cc, ToolBar.cc, annotation-dialog.cc, qt-graphics-toolkit.cc, documentation-bookmarks.cc, documentation-bookmarks.h, documentation-dock-widget.h, documentation.cc, documentation.h, dw-main-window.h, files-dock-widget.cc, files-dock-widget.h, find-files-dialog.cc, find-files-model.cc, gui-preferences-dw.h, gui-preferences-ed.h, gui-preferences-global.h, gui-settings.h, interpreter-qobject.cc, led-indicator.cc, 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, octave-qscintilla.cc, octave-qscintilla.h, main-window.cc, main-window.h, octave-dock-widget.cc, octave-dock-widget.h, octave-qobject.cc, octave-qobject.h, octave-qtutils.h, qt-interpreter-events.cc, release-notes.cc, resource-manager.cc, set-path-dialog.cc, settings-dialog.cc, settings-dialog.h, shortcut-manager.cc, shortcut-manager.h, tab-bar.cc, tab-bar.h, variable-editor-model.cc, variable-editor-model.h, variable-editor.cc, variable-editor.h, workspace-model.cc, workspace-view.cc, mkoctfile.in.cc, octave-config.in.cc: Style check C++ files in src/ and libgui/ ahead of 7.1 release.