non-recursive WITH clause support

Here's an updated patch that fixes the bug I had. This is now functional basic
non-recursive WITH clause support.

 http://community.enterprisedb.com/recursive/with-pg82stable-v2.patch.gz

It's a pretty short simple patch as is; it just directly inlines any WITH
clauses as if they had been written as subqueries. We'll have to do something
much more clever to get recursive queries to work but for non-recursive
queries that's sufficient.

Example:

postgres=# with a as (select 1 as x) select * from (select * from a) as x;
 x
---
 1
(1 row)




--
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com