updated patch for selecting large results sets in psql using cursors

Hi there,

here comes the latest version (version 7) of the patch to handle large
result sets with psql. As previously discussed, a cursor is used
for SELECT queries when \set FETCH_COUNT some_value > 0
(defaults to 100 if FETCH_COUNT is set with no value).

Comparing to the previous version, the patch actually got smaller and is
less invasive, because I doesn't have to deal with a new command and
can share some more code with SendQuery() in common.c.

Bye,
Chris.

--
Chris Mair
http://www.1006.org