Patch to readelf dwarf2 support

[DJ Delorie]

> BTW, Jason, would you mind submitting and checking in your recent
> demangling patches for libiberty in the `src' tree too?

I automatically take care of these (in my role as libiberty
maintainer) if they don't get checked into both places within a short
time, even though the master demangler files are individually
maintained by <not-me>.  It would have happened yesterday, but I was
pretty busy yesterday.  It happened today, although I see yet another
patch to merge :)