Remove "Exit" from commands menu, it causes crashes when opening the
OSD next time after exiting the plugin.

diff -up sudoku-0.2.0/commands.cpp~ sudoku-0.2.0/commands.cpp
--- sudoku-0.2.0/commands.cpp~	2008-03-22 04:00:00.000000000 +0200
+++ sudoku-0.2.0/commands.cpp	2008-03-22 14:11:15.000000000 +0200
@@ -43,7 +43,6 @@ CommandMenu::CommandMenu() :
   Add(new Command(hk(tr("Save the puzzle")),       &Menu::save));
   Add(new Command(hk(tr("Reset the puzzle")),      &Menu::reset));
   Add(new Command(hk(tr("Open setup menu")),       &Menu::open_setup));
-  Add(new Command(hk(tr("Exit")),                  &Menu::exit));
   command = NULL;
 }