Making Errors errors

[Max Haughton]

It has been discussed in a different thread (Making throwing an 
error an instant failure, catching Error etc.)

I am starting to put together a patch to try out this behaviour, 
what do we actually want it to do - should it call a user 
specified handler, druntime, c etc.?

The rationale makes perfect sense (Errors should indicate 
something has gone wrong, the program is in an invalid state - by 
definition you cannot recover), but the exact behaviour must be 
specified.