Fixed #10467 -- Fixed generated INSERT SQL for PostgreSQL 8.1 and earlier.

I introduced a bad regression in r10029, forgetting to check that some
syntax was supported. For now, you can't use autocommit=True with 8.1
and earlier (it's still available for later versions). I'll fix the
broader issue later and re-enable it for those versions, but I want to
get the SQL regression for the default path out of the code right now.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10035 bcc190cf-cafb-0310-a4f2-bffc1f526a37