gui: Add select all menu (Bug #41797) * libgui//qterminal/libqterminal/QTerminal.h: Add selectAll popup menu and virtual function. * libgui/qterminal/libqterminal/unix/QUnixTerminalImpl.cpp,h: Add selectAll function. * libgui/qterminal/libqterminal/unix/TerminalView.cpp,h: add selectAll function. * libgui/qterminal/libqterminal/win32/QWinTerminalImpl.cpp,h: Add selectAll function. * libgui/src/documentation-dock-widget.cc,h: Add selectAll function. * libgui/src/files-dock-widget.cc,h: Add selectAll function. * libgui/src/history-dock-widget.cc,h: Add selectAll function. * libgui/src/m-editor/file-editor-tab.cc,h: Add select_all function and signal. * libgui/src/m-editor/file-editor.cc,h: Add request_selectall and selectAll function, add Edit->select all menu. * libgui/src/main-window.cc: add selectAll function, selectAll menu. * libgui/src/octave-dock-widget.cc,h: Add virtual selectAll function and connect to mainwindow selectall signal. * libgui/src/qtinfo/webinfo.cc,h: Add selectAll function. * libgui/src/workspace-view.cc,h: Add selectAll function.

To cite GNU Octave in publications use:

  John W. Eaton, David Bateman, and Søren Hauberg (2009).  GNU Octave version
  3.0.1 manual: a high-level interactive language for numerical computations.
  CreateSpace Independent Publishing Platform.  ISBN 1441413006,
  URL http://www.gnu.org/software/octave/doc/interpreter/

A BibTeX entry for LaTeX users is:

  @book{,
    author    = {John W. Eaton and David Bateman and S\oren Hauberg},
    title     = {{GNU Octave} version 3.0.1 manual: a high-level interactive language for numerical computations},
    publisher = {CreateSpace Independent Publishing Platform},
    year      = {2009},
    note      = {{ISBN} 1441413006},
    url       = {http://www.gnu.org/software/octave/doc/interpreter},
  }

We have invested a lot of time and effort in creating GNU Octave, please cite it
when using it.  See also `citation pkgname' for citing Octave packages.