Now that states have a complete set of members, the linked list of

Now that states have a complete set of members, the linked list of
shifts is useless: just fill directly the state's shifts member.
* src/state.h (shifts): Remove the `next' member.
* src/LR0.c (first_state, last_state): Remove.
Adjust the callers.
(augment_automaton): Don't look for the shifts that must be added
a shift on EOF: it is those of the state we looked for!  But now,
since shifts are attached, it is no longer needed to looking
merely by its id: its number.