Remove useless final states; calculate fallback states more accurately.

Remove useless final states; calculate fallback states more accurately.

Removing useless final states allows some further optimizations
which would otherwise be impossible (see the changed tests for
example).

However, removing useless final states revealed previously hidden
defects in calculating fallback states: in some tests spurious
new 'yyaccept' values appeared. It turned out that we used incorrect
(imprecise, too pessimistic) algorithm to calculate fallback states:
the given state was considered to be fallback state if it was final
and had transitions to non-default and non-final states. This
algorithm erroneousl captures cases when all paths from the given
state are accepting and long enough (longer than one transition).
The new algorithm to find fallback states uses information obtained
by rule liveness analyses (reachability of "none-rule" in particular).

Some important tests changed a lot; skeleton says the changes are
correct (as well as manual looking into the changes).