NANO_SMALL #ifdef, since the tiny version of nano doesn't support
reverse searching; also, turn the USE_REGEXP flag off during spell
checking in order to avoid a potential segfault


git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@1979 35c25a1d-7b9e-4130-9fde-d3aeb78583b8