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