Re: Add schema-qualified relnames in constraint error messages.

> most recent error in verbose mode, without making a permanent session

> state change.  Something like
>
> regression=# insert into bar values(1);
> ERROR:  insert or update on table "bar" violates foreign key constraint "bar_f1_fkey"
> DETAIL:  Key (f1)=(1) is not present in table "foo".

> regression=# \saywhat