This is an amalgamation of several fixes:
- Undo the default empty string in die_name(); this syncs with upstream. Many things check the return of die_name() for NULL and these cases must trigger or else other bugs will occur.
- die_sou_resolve(): Rather than crash, consider a SOU as unresolvable if its type descriptor references a currently unknown DIE. The top-level will retry until it either finds the type or it will bail.
- Don't require function arguments to have names. C/C++ don't require this, and CTF doesn't care if there isn't one, because it already has arg0/arg1/.../argN and args.
- Ensure that the variadic argument can't be reached in the second loop.
- Emit the 'function has %d arguments' debug message even if the function had no arguments, for information purposes and also inform whether the function is variadic.