MFC r317075: Update ELF Tool Chain to upstream r3520
Highlights of changes between r3490 and r3520:
- Improve C++ demangling
- Improve compatibility with Binutils tools wrt. error messages
- Handle additional types/sections/etc. in readelf and elfdump
- addr2line, cxxfilt: use setvbuf to set line buffering for filter use
Also MFC r317076, version bump.
Sponsored by: The FreeBSD Foundation