Make showreview comment numbering consistent

[fekblom]

Previously, in a thread with the original comment + 1 extra comment that had been read by the user Critic would display the number of comments as: 1 reply. Adding a second reply (bringing the total number of comments to 3) would be displayed to the user as: 1 out of 3 unread. After marking that thread as read it will go back to display as: 2 replies.

This commit make the "total" number always refer to the number of replies instead of alternating between the number of replies and the number of comments in total (including the original one).

[jensl]

Reviewed in https://critic-review.org/r/361.