Re: BUG #18468: CREATE TABLE ... LIKE leaves orphaned column reference in extended statistics

I wrote:
> We don't know the column mapping there, either.  What we need to have
> our hands on is the "attmap" computed in expandTableLikeClause, and
> then we can pass the stats expressions through map_variable_attnos().

> I think this might not need to be a really large patch, but it
> definitely has to change where generateClonedExtStatsStmt is
> called from.  I can have a go at it if Tomas doesn't want to.

Yeah, this doesn't require a whole lot more than moving the
processing in transformTableLikeClause to expandTableLikeClause.

I chose to get rid of transformExtendedStatistics, because not
only is there nothing for it to do, there will never be any
statements for it to do nothing to.