printing Throwables in druntime

[David]

currently the class Throwable has a member toString which basically 
generates the pretty stacktrace: 
https://github.com/D-Programming-Language/druntime/blob/master/src/object_.d#L1337

Now, I tried to override that toString function to get my own 
Exception-Body, but it just didn't call my overriden toString, so 
looking at rt/dmain.d where the Exceptions are print:

https://github.com/D-Programming-Language/druntime/blob/master/src/rt/dmain2.d#L530

The Throwable.toString method is never used, but basically reimplemented 
in these print* functions.

What hinders us from replacing:

`print(t);`

with:

`console(t.toString())`?

The only difference I can see is the "bypassed" exception-stuff, but I 
would rather implement that in Throwable.toString. This would also fix 
my problem of not beeing able to change the body of an Exception.