Set attstattarget to -1 for all system catalog columns. All but a few

of the entries used to be zero, which I think I had deliberately done in
the name of saving cycles during ANALYZE, but it was really a rather
foolish decision.  Some of the more complex views in information_schema
were getting really bad plans for lack of statistics on the columns they
were joining over.

I'm not forcing an initdb for this, but I think there will be one soon
anyway to repair some bugs in the information_schema views.