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

PR: 218395
MFC after: 2 weeks
Relnotes: Yes
Sponsored by: The FreeBSD Foundation