BUG #13620: Streaming replication process titles should use zero padding for TX ids.

The following bug has been logged on the website:

Bug reference:      13620
Logged by:          Jürgen Strobel
Email address:      juergen+postgresql@strobel.info
PostgreSQL version: 9.4.4
Operating system:   Linux, REL6
Description:


Hello,

I frequently use "watch ps xf" to monitor server restarts etc., it's really
a great, simple and effective tool. But there is a minor formatting issue,
which has caused considerable confusion not only for me already.

For example:

postgres$ ps xf
... /usr/pgsql-9.4/bin/postmaster -D /mnt/db/.../data
... \_ postgres: startup process   recovering 00000005000004B500000007
... \_ postgres: wal receiver process   streaming 4B5/78A2C80
... \_ postgres: wal sender process replication [local] streaming
4B5/78A2C80

>From the last 2 lines I would guess at first glance that those processes are
streaming segment "78" at the moment, while they really are at segment "07".
It should be trivial to zero-pad this id.

Best regards,
Jürgen