Remove trailing hash value from demangled Rust symbol names

[jasonrhansen]

When demangling Rust symbol names, binutils addr2line removes the trailing hash value. The rustc_demangle crate allows Demangle to be formatted with or without the hash. I think this crate should match the behavior of binutils.

From rustc-demangle:

// With hash
assert_eq!(format!("{}", demangle("_ZN3foo17h05af221e174051e9E")), "foo::h05af221e174051e9");
// Without hash
assert_eq!(format!("{:#}", demangle("_ZN3foo17h05af221e174051e9E")), "foo");

[jonhoo]

@main-- awesome! Can we get a minor release with that change too pretty please? :p

[main--]

cc @fitzgen @philipc

[philipc]

Published 0.8.0. Had to be a major release because object is part of the public API.