committing inside cursor loop

Here is a patch that allows COMMIT inside cursor loops in PL/pgSQL.  As
alluded to in earlier threads, this is done by converting such cursors
to holdable automatically.  A special flag "auto-held" marks such
cursors, so we know to clean them up on exceptions.

This is currently only for PL/pgSQL, but the same technique could be
applied easily to other PLs.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services