oops; in do_output(), properly allow wrapping when we insert a tab, for

oops; in do_output(), properly allow wrapping when we insert a tab, for
consistency; this is incompatible with Pico, but Pico doesn't wrap
properly when other control characters are on a line, either, so its
behavior with regard to tabs is apparently a bug; besides, we wrap at
all other blank characters, including multibyte ones, so we shouldn't
make an exception for tabs

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2491 35c25a1d-7b9e-4130-9fde-d3aeb78583b8