Restore default topic title links in subsilver2

Subsilver2 topic titles were changed to take the user to the first unread posts, instead of the first topic in ticket 11969.

This was reverted for Prosilver (in ticket 12300), but subsilver2 was not yet reverted back to original functionality.

Not to re-inflame the debate, but this was all due to prosilver having a small icon issue on mobile touch devices. This has been solved for prosilver2. So subsilver2, which does not suffer the same problem badly as prosilver did, should be restored to original functionality.