[tl] Thread Symbiotics V1.0.3

Description: Make more threads which link to an existing thread.

Symbiotic threads work like the current thread redirect but with few differences:

• Symbiotic threads is permanently redirects
• Symbiotic threads have last post info and display as normal threads in thread list.
• One existing thread can have more symbiotic
• Automatically update symbiotic thread stats when the source thread updated.

This allows for one thread to appear in many forums with very little give away from what forum it originated.
Any thread updates bump the symbiotic thread up in the regular sort by post date.
The symbiotic thread acts like a regular thread even though it originates elsewhere.

It follows sticky thread behavior.