Change pg_stat_all_tables and sister views to put the recently-added

Change pg_stat_all_tables and sister views to put the recently-added
vacuum/analyze timestamp columns at the end, rather than at a random
spot in the middle as in the original patch.  This was deemed more usable
as well as less likely to break existing application code.  initdb forced
accordingly.  In passing, remove former kluge for initializing
pg_stat_file()'s pg_proc entry --- bootstrap mode was fixed recently
so that this can be done without any hacks, but I overlooked this usage.