Hmm, maybe I'm mistaken - before I'd solved a shutdown crash by adding it.  Now that I check `PSP_Shutdown()` again it doesn't *seem* to kill the jit.  Still, it does free the memory maps, so it's kinda the same issue.

Consider that the emulation thread is currently in a function body.
The user selects RESET or STOP.
PSP_Shutdown() calls Memory::Shutdown(), which ultimately calls UnmapViewOfFile().
Thread switches back to emulation.  It continues along, not knowing anything, to a `sw` or `lw` jitted instruction.
Thread gets a segfault accessing the above-freed memory.

The purpose of `Core_WaitInactive()` was to prevent these cases.  It waits until jit gets back to the run loop, where it's safe to start destroying things.  Any other time can cause crashes.

-[Unknown]