C++ exceptions doesn't work on any ELF port using the dwarf2 unwind
mechanism, but everything works fine using set-jump/long-jump exceptions.
So I'm going to let all ELF ports using sjlj exceptions (by adding a line
#define DWARF2_UNWIND_INFO 0 in the relevant gcc configuration files.)

This constituetes an ABI change, but as I understands it, it will only
affect the actual throwing of excetions (and that segfalts without this
change anyway...) Sjlj is slower than the other exception mechanism, but
they work now. I will make sure that we use the faster mechanism when we
switch to gcc 3.0 (since it will involve an API change anyway.)

So I just want to make sure people don't think this is a stupid thing to
do. I'll make this change Thursday unless someone complains before that.

   /Krister