Re: Remove Deprecated Exclusive Backup Mode

The deprecated exclusive mode promises to make a difficult problem
simple but doesn't live up to that promise. That's why it was replaced
externally in 9.6 and why pg_basebackup has not used exclusive backups
since it was introduced in 9.2.

Non-exclusive backups have been available since 9.6 and several
third-party solutions support this mode, in addition to pg_basebackup.

The recently introduced recovery changes will break current automated
solutions so this seems like a good opportunity to make improvements on
the backup side as well.

I'll submit a patch for the 2019-01 commitfest.