Removed a TODO item.

TODO

-* LRijkstra: see if the forward search could be removed by just adding
-  one more trie, rooted at the initial state, which covers all of the
-  automaton?
-
 * Another crazy idea: if we had a special "void" non-terminal symbol,
   we could use it as a parameter, which would allow us to make extensible
   definitions. (Any production that contains void would be removed after