If the backup cannot map a group to a name it stores the group in the manifest as false then uses either the owner of $PGDATA to set the group during restore or failing that the group of the current user. This logic was not working correctly because the selected group was overwriting the user on restore leaving the group undefined and the user incorrectly set to the group. (Reported by Jeff McCormick.)
The existing static files would not work with 32-bit or big-endian systems so create functions to generate these files dynamically rather than creating a bunch of new static files.
* Exclude contents of pg_snapshots, pg_serial, pg_notify, and pg_dynshmem from backup since they are rebuilt on startup.
* Exclude pg_internal.init files from backup since they are rebuilt on startup.
