have edit_refresh() call edit_update() with NONE when smooth scrolling

have edit_refresh() call edit_update() with NONE when smooth scrolling
is on so that smooth scrolling applies everywhere instead of just to the
movement functions, fix a potential infinite loop when edit_update() is
called with NONE and current_y is greater than (editwinrows - 1), and
have do_para_begin() and do_para_end() maintain current_y as
do_justify() does (and as they did before)

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@1917 35c25a1d-7b9e-4130-9fde-d3aeb78583b8