Re: pg_dumpall dumps global objects with --statistics-only or --no-schema

+1, pending resolution of the defaults issue.

At first glance, this looks like a good candidate for the the same refactor that we did to pg_dump in 96a81c1be929, where we abandoned using the schema_only and data_only flags to determine what should be dumped in favor of dumpSchema, dumpData, and eventually dumpStatistics. This made for a cleaner interface because each test was described in terms of what was wanted, not in terms of the opposite being not the case, and all of the double/triple-negative boolean backflips were concentrated right after the options conflict resolutions.

However, all prospective do_this_thing branches are used exactly once, so there is no code savings to be had and no clarity to be gained, so this patch is fine as is.