update psql versionned docs URLs to latest debian (11)

tsa/howto/postgresql.mdwn

@@ -17,7 +17,7 @@ is like any other Debian machine:
 
     sudo -u postres psql
 
-This drops you in a [psql shell](https://www.postgresql.org/docs/9.6/app-psql.html) where you can issue SQL queries
+This drops you in a [psql shell](https://www.postgresql.org/docs/11/app-psql.html) where you can issue SQL queries
 and so on.
 
 Howto
@@ -75,7 +75,7 @@ Same with databases:
         END DESC -- nulls first
         LIMIT 20;
 
-Source: [PostgreSQL wiki](https://wiki.postgresql.org/wiki/Disk_Usage). See also [the upstream manual](https://www.postgresql.org/docs/9.1/disk-usage.html).
+Source: [PostgreSQL wiki](https://wiki.postgresql.org/wiki/Disk_Usage). See also [the upstream manual](https://www.postgresql.org/docs/11/disk-usage.html).
 
 Running a full backup
 ---------------------
@@ -109,7 +109,7 @@ location on the new server. The downside is it might be more difficult
 to deploy and diagnose, as it has more moving parts.
 
 Both procedures are adaptations of the [official recovery
-procedure](https://www.postgresql.org/docs/9.3/continuous-archiving.html#BACKUP-PITR-RECOVERY), which can be refered to for more information.
+procedure](https://www.postgresql.org/docs/11/continuous-archiving.html#BACKUP-PITR-RECOVERY), which can be refered to for more information.
 
 Indirect restore procedures
 ---------------------------
@@ -183,7 +183,7 @@ server to the database server and restores from those.
         restore_command = 'cp /var/lib/postgresql/restore/subnotablie/main.WAL.%f %p'
 
     You can specify a specific recovery point in the `recovery.conf`,
-    see the [upstream documentation](https://www.postgresql.org/docs/9.3/recovery-target-settings.html) for more information.
+    see the [upstream documentation](https://www.postgresql.org/docs/11/recovery-target-settings.html) for more information.
 
  10. Then start the server and look at the logs to follow the recovery
      process:
@@ -325,7 +325,7 @@ information on how to pick a restore procedure.
        (e.g. `main`, generally)
 
     You can specify a specific recovery point in the `recovery.conf`,
-    see the [upstream documentation](https://www.postgresql.org/docs/9.3/recovery-target-settings.html) for more information. Also
+    see the [upstream documentation](https://www.postgresql.org/docs/11/recovery-target-settings.html) for more information. Also
     make sure the file is owned by postgres:
 
         $EDITOR /var/lib/postgresql/9.6/main/recovery.conf
@@ -435,7 +435,7 @@ Backup design
 -------------
 
 We use upstream's [Continuous Archiving and Point-in-Time Recovery
-(PITR)](https://www.postgresql.org/docs/9.3/continuous-archiving.html)
+(PITR)](https://www.postgresql.org/docs/11/continuous-archiving.html)
 which relies on postgres's "write-ahead log" (WAL) to write regular
 "transaction logs" of the cluster to the backup host. (Think of
 transaction logs as incremental backups.) This is configured in