Here is a patch for a couple of tiny issues I encountered in ox-ascii.el
while debugging ox-icalendar.el.  Explanation:

1) There is no function called `org-ascii-footnote-definition' (though
it looks like maybe there once was?), so I changed a reference to it to
`ignore' to be more explicit.

I'm not sure if this is the right thing to do -- maybe the point was to
let the user define such a function if she wishes?  That however would
be inconsistent with the comment that such definitions are ignored (see
below).

2) A tiny change to the comment explaining why there is no such
function: footnote definitions are ignored because they are compiled by
`org-ascii-inner-template', not `org-ascii-template'.

Best,
Richard