Comment 5 for bug 1717714

OK, so if http://man7.org/linux/man-pages/man5/proc.5.html says:

```
On 64-bit systems, pid_max can be set to any value up to 2^22 (PID_MAX_LIMIT, approximately 4 million).
``

Its 4194304, so I will propose adding one more bulk of expressions for seven-digit PID, stating with [1-4].