overhaul the high-level input routines for the statusbar to make them

overhaul the high-level input routines for the statusbar to make them
more flexible, among other things, and add UTF-8 support to them in the
process; also update the copyright years of the modified files

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2210 35c25a1d-7b9e-4130-9fde-d3aeb78583b8