parsergen: store reduction information separate from states.

parsergen: store reduction information separate from states.

There are more states than reductions (aka productions) so storing the
reduction data in the state table results in a lot of duplication - and
wasted space as some states have no reduction.

So create a separate table of reduction information.  This will also
make it easier to allow a state to have multiple reductions with LALR
and canonical-LR grammars.

Signed-off-by: NeilBrown <neil@brown.name>