pg_autovacuum patches

Hello,

I noticed that there have been a few patched submitted for pg_autovacuum
that have not been applied, so I applied them locally and tested them on
my Fedora box.  I am resubmitting them as one single patch.

Included in the attached patch:

Brian Hurt's patch that fixed the truncate bug by referencing a table
oid rather than it's relfilenode.

Craig Boston's patch that fixes crashes on FreeBSD related to
uninitialized variables.

A quick patch by me to remove a log_entry call inside init_table_info()
that was used for debugging by me during development and I left in by
mistake.

Please apply this patch to both HEAD and 7.4.

Thanks much,

Matthew O'Connor