Some tests for basic thread funcs

This adds a few additional tests, but also changes common.

The change to common is I went ahead and put `schedf()` there.  Since it's inline everywhere else, it should still compile elsewhere.  I think this is the correct way to test scheduling most of the time.

It also tests `sceKernelReferThreadStatus()` and `sceKernelStartThread()`, although there's always more to figure out.  Like the extra value in thread status after 2.60.

There's also apparently still a scheduling bug, which these tests point out neatly (after starting a lower priority thread, the caller doesn't get scheduled upon return...)

-[Unknown]