error and undefined should print a location

[augustss]

The Control.Exception.assert function has a very nice hack so it prints a location together with the message. Could we please have that feature for 'error' and 'undefined' as well?

I just had the case where in one of 83 installed packages some idiot has an error message that just says 'dataTypeConstrs', which makes it very tedious to figure out what to fix. Yes, I can recompile everything for profiling, but that takes another two hours, which is why I'd prefer location information. (BTW, hbc had location info for those.)