MF11 r320685: Update to ELF Tool Chain snapshot at r3561

MF11 r320685: Update to ELF Tool Chain snapshot at r3561

This update is primarily bug fixes in C++ symbol demangling, including:

- rvalue reference
- builtin type auto and decltype(auto)
- revamped support for function return types
- formatting fixes
- omit void when its the only param
- ref-qualifiers and others in function types
- type qualifiers in pointer-to-member function types
- incorrect handling regarding CV-qualifiers in function types
- ref-qualifier found in nested-name
- properly handle <name> ::= <substitute><template-args>
- make sure that nested function name is not a substitute candidate
- correctly handle expression in template args
- skip unknown substitution abbreviations

Also r320663 libelftc: bump version, tracking import in r320343

Approved by:	re (gjb)
Sponsored by:	The FreeBSD Foundation