jdbc driver patch: refcursor types, cursor based querys.

(Sorry if people have seen this before, I've tried to post it several
times without success: this is my last try before talking to the
admins).

The attached patch provides several things:

1. it allows refcursor ResultSet's to be obtained from a stored proc
returning a refcursor value. The actual value returned is:

org.postgresql.PGRefCursorResultSet

which represents a refcursor as per discussions I had with Barry.
In essence it looks exactly like a ResultSet but is not actually
fetched until next() is called on it.

2. cursor based querys allowing massive fetches.
Calling Statement.setFetchSize(x) causes the driver to use a cursor
and a forward fetch of size x.

3. simplification of the calling routines.
The QueryExecutor has been made more static. Simplifications were
made to reduce the number of method calls.

It should be applied to the latest source tree (which is 7.3.1 I believe).

Note that as far as 3 is concerned I have some more ideas that came
out of discussions about re-(java)packaging with Barry. These can
wait until this patch gets accepted (or not!).

Thanks, and Merry Christmas.

Nic