verbose terminate handler

[Joerg Richter]

I had today a crash with output like this:

pure virtual function called
terminate called after throwing a `...'
  what(): ...

It took me a little bit to discover that there wasn't actually any uncaught exception but a pure virtual call deep inside a catch. A little bit confusing if you don't know that this 'terminate called ...'-thing doesn't alway indicate an uncaught exception.

   Joerg