Allow kdel to be rebound
Add note about rebinding kdel to backspace for those using OSX or PuTTY to connect to remote Linux machines in nanorc.sample.in

When undoing text deletes, move current_x to proper location



git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@4281 35c25a1d-7b9e-4130-9fde-d3aeb78583b8