Thread list

Adds a list of all (emulated) threads to the disassembly window. It's part of the tab rotation, and updated when debug mode is entered. Double clicking on a thread will jump to its PC.

![psp6](https://f.cloud.github.com/assets/4809758/739576/b896570c-e35d-11e2-960f-e199bce3ed0c.png)