Throwing InvalidMemoryOperationError

[Adam D. Ruppe via Digitalmars-d]

If int 3 doesn't work for some reason btw, you could always just 
deliberately write to a null pointer and trigger a segfault in 
the overridden function, would have the same result in the 
debugger.

I feel like this onError thing is meant to be overridable by 
importing core.exception too, but I don't see that in the source. 
The linker-based override definately works today though!