Ok, this fixes three things:

1. It seems (from tests submitted by two people with JBuilder) that
   JBuilder expects a responce from ResultSetMetaData.getPrecision() &
   getScale() when used on non numeric types. This patch makes these
   methods return 0, instead of throwing an exception.

2. Fixes a small bug where getting the postgresql type name returns null.

3. Fixes a problem with ResultSet.getObject() where getting it's string
   value returns null if you case the object as (PGobject), but returns
   the value if you case it as it's self.