maint: Fix various problems with GPL copyright statements. * libgui/qterminal/libqterminal/QTerminal.cc, libgui/qterminal/libqterminal/QTerminal.h, libgui/qterminal/libqterminal/win32/QTerminalColors.cpp, libgui/qterminal/libqterminal/win32/QTerminalColors.h, libgui/qterminal/libqterminal/win32/QWinTerminalImpl.cpp, libgui/qterminal/libqterminal/win32/QWinTerminalImpl.h: Replace "Foobar" with "This program" in GPL statement. * scripts/linear-algebra/linsolve.m: Replace "This program" with "Octave" in * GPL statement. * scripts/miscellaneous/getappdata.m, scripts/miscellaneous/isappdata.m, scripts/miscellaneous/rmappdata.m, scripts/miscellaneous/setappdata.m: Add "This file is part of Octave" line. Replace "This program" with "Octave" in GPL statement. Update GPL version to 3. * scripts/plot/util/copyobj.m, scripts/plot/util/hdl2struct.m, scripts/plot/util/struct2hdl.m, scripts/polynomial/ppder.m, scripts/polynomial/ppint.m, scripts/polynomial/ppjumps.m, scripts/sparse/bicg.m, scripts/strings/untabify.m: Replace "This program" with "Octave" in GPL statement.

--- a/scripts/plot/util/hdl2struct.m
+++ b/scripts/plot/util/hdl2struct.m
@@ -1,11 +1,13 @@
 ## Copyright (C) 2012-2013 pdiribarne
 ##
-## This program is free software; you can redistribute it and/or modify
+## 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.
 ##
-## This program is distributed in the hope that it will be useful,
+## 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.