change the behavior of Esc Esc [3-digit number from 000 to 255] so that

change the behavior of Esc Esc [3-digit number from 000 to 255] so that
it enters the byte with that value regardless of whether we're in UTF-8
mode or not, and update the help text to mention this; this will allow
searching for and replacing raw bytes with their equivalent multibyte
sequences as entered using verbatim input

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2653 35c25a1d-7b9e-4130-9fde-d3aeb78583b8