AllowEmptyInput is on by default AFAIK. If you want to disable it, add it to the
ServerFlags section and give it a off/false/0 value, case insensitive.
I may be wrong so don't quote me. But I think all these options have been removed from
xorg.conf and should be configured through HAL (somewhere like
/usr/local/etc/hal/fdi/policy/).
Or maybe try with setxkbmap. It should work and give you the least headaches.