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

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