Add minor clarifications to some threads tests

This made it easier to test what/why/how.  The threads/threads/terminate and threads/scheduling/scheduling tests don't pass, mostly due to timing reasons, but they're "generally" correct with the latest pull.

I've set in PPSSPP (probably not exactly the ram size I have available):
```
Memory::g_MemorySize = 0x03B00000;
```

Which makes these tests pass (since I'm running them with psplink on a non-phat.)  Some of them (thread stack allocation etc.) don't pass out of the box currently.  Not sure if I should trim things out of the tests, or what...

-[Unknown]