"CLUSTER VERBOSE" tab completion

tab completion will add "USING" after CLUSTER VERBOSE, as if VERBOSE
were the name of a table.

Instead of just making it not do the wrong thing, I tried to make it
actually do the right thing.

It doesn't fill in the VERBOSE for you, you have to type that in full,
but then it completes table names afterward (and USING and index names
after that)

Cheers,

Jeff