v1.21: Improved Info Output and SSH Port Option

Bug Fixes:

* The archive_status directory is now recreated on restore to support PostgreSQL 8.3 which does not recreate it automatically like more recent versions do. (Reported by Stephen Frost.)
* Fixed an issue that could cause the empty archive directory for an old PostgreSQL version to be left behind after a stanza-upgrade. (Fixed by Cynthia Shang.)

Features:

* Modified the info command (both text and JSON output) to display the archive ID and minimum/maximum WAL currently present in the archive for the current and prior, if any, database cluster version. (Contributed by Cynthia Shang.)
* Added --backup-ssh-port and --db-ssh-port options to support non-default SSH ports. (Contributed by Cynthia Shang.)

Refactoring:

* Retry when S3 returns an internal error (500).
* Add bIgnoreMissing parameter to Local->manifest().

test/expect/help-help-001.log

@@ -85,6 +85,7 @@ Repository Options:
   --backup-config           pgBackRest backup host configuration file
 [default=/etc/pgbackrest.conf]
   --backup-host             backup host when operating remotely via SSH
+  --backup-ssh-port         backup server SSH port when backup-host is set
   --backup-user             backup host user when backup-host is set
 [default=backrest]
   --repo-path               repository path where WAL segments and backups