[Issue 15886] Add an uncaught exception handler

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15886

--- Comment #2 from Marenz <dmdtracker at supradigital.org> ---
The bigger problems I found are that you can't set rt_trapExceptions to 0 from
inside your program or through environment variables / command line parameters.

So you never actually have a core dump generated other then when started
through a debugger (the comments for that variable claim a debugger would set
it to 0).

Another problem is that fibers also have an exception trap so the switch
doesn't even have an effect there. 

That's why I created 

https://github.com/D-Programming-Language/druntime/pull/1538

and 

https://github.com/D-Programming-Language/druntime/pull/1537

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