Exceptions with dwarf2 unwind

[Jim Wilson]

	I'm not sure if anyone is using dwarf2 unwind EH on mips ports
	yet.  Anyone want to chime in with a definitive answer?

The mips/irix6 port was the first one to support dwarf2 debug info, and I
believe it was also the first port to support dwarf2 unwind EH.  Of course,
what works for irix6 does not necessarily work for other mips ports.

Considering how different vxworks is, it isn't too surprising that
additional work might required to get it working there.

Jim