I've been getting a lot of segfaults from using associative
arrays recently. The faults happen seemingly at random, and from
pretty mundane stuff like `if(auto x = y in z)` that run very
often:
```
Segmentation fault.
#0 0x0000555555670f4a in rt.aaA.Impl.findSlotLookup(ulong, scope
const(void*), scope const(TypeInfo)) inout ()
#1 0x0000555555661662 in _aaInX ()
```
I suspect that this is because they've all been placed inside
`__ghared` structs. Are DRuntime's AAs simply incompatible with
`__gshared`? Do they need to be marked as `shared` to prevent
these shenanigans?
