add editor prefs for forcing coding standards (bug #57860, bug #57861) * gui-preferences-ed.h: add new editor preferences for removing trailing spaces and forcing a newline at end of the file when saving the file. * file-editor-tab.cc (eol_string): new method for determining the current end of line string; (do_save_file): depending on the user preferences, rmove trailing spaces and/or add a newline at the end before saving the file * file-editor-tab.h: new private method eol_string * settings-dialog.cc (settings_dialog): initialize new check boxes for handling trailing spaces and newline at end of file with prefs from the settings file; (write_changed_settings): write checked states of new check boxes into the settings file * settings-dialog.ui: new check boxes for handling trailing spaces and newline at end of file

To cite GNU Octave in publications use:

  John W. Eaton, David Bateman, Søren Hauberg, Rik Wehbring (2019).
  GNU Octave version 5.2.0 manual: a high-level interactive language for
  numerical computations.
  URL https://www.gnu.org/software/octave/doc/v5.2.0/

A BibTeX entry for LaTeX users is:

  @manual{,
    title     = {{GNU Octave} version 5.2.0 manual: a high-level interactive language for numerical computations},
    author    = {John W. Eaton and David Bateman and S{\o}ren Hauberg and Rik Wehbring},
    year      = {2020},
    url       = {https://www.gnu.org/software/octave/doc/v5.2.0/},
  }

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.