per DB's patch (with a few updates of mine), convert the shortcut list

per DB's patch (with a few updates of mine), convert the shortcut list
functions and most related functions to return void instead of int, as
the return values of all those functions are essentially unused; also
add a few related miscellaneous cleanups

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@1836 35c25a1d-7b9e-4130-9fde-d3aeb78583b8