Correct sceKernelThreadmanIdList behavior

This function is used by the God Eater games and a few others.  I'm not sure exactly how these games use it, so this may not affect behavior much.

 * The return value was previously always 0, which turns out to be incorrect.
 * Other object types should be working (not each carefully tested yet.)  Before it always returned an error.
 * The thread classes (sleeping, dormant, etc.) now work.  Before it always returned an error.
 * A NULL pointer and 0 size now works to get a count, which did not work before.

Putting finishing touches on the test (which doesn't pass currently due to psplink objects existing, trying to decide the best way to screen those out.)

-[Unknown]