Slight adjustment to forum topic URLs

Apologies for any inconveniences, but I've decided before the forums get too large to change the URLs of individual topic posts.

Old: /forums/topics/<title>
New: /forums/<forum>/<category>/<title>

As an example, the latest post on the Meerkat beta went from:

/forums/topics/meerkat-12b2

to:

/forums/mac-os-x-products/meerkat/meerkat-12b2

This was partly because I only recently discovered how to easily do this, and partly to keep the URL namespace clear and divided by the actual forum and category under which the discussion is taking place.

Again, sorry for any inconveniences. The search index should be updated to reflect these changes.