Re: Materialized views WIP patch

Here is a new version of the patch, with most issues discussed in
previous posts fixed.

I've been struggling with two areas:

 - pg_dump sorting for MVs which depend on other MVs
 - proper handling of the relisvalid flag for unlogged MVs after recovery

I've been hacking at the code in those areas without success;
what's here is the least broken form I have, but work is still
needed for these cases. Any other problems are news to me.

In addition, the docs need another pass, and there is an open
question about what is the right thing to use for TRUNCATE syntax.

-Kevin