node/%node/revisions revisions should be sorted by vid instead of timestamp

The list of revisions on this page is sorted by timestamp (desc), it would be better to sort the list by vid (desc). This shouldn't be a significant change unless you're using module revision moderation.

When using revision moderation you want to see revisions with a higher vid than the current node above the current node in the list regardless of timestamps. Without this change new unapproved revisions can appear lower than the current revision in the list which can be confusing.

This patch only changes the sort field for node/%node/revisions.

A further improvement would be to colour code unapproved revisions but I'll leave that for now.