Update the backtrace crate
Update the backtrace crate

https://github.com/rust-lang/backtrace-rs/pull/437 fixed backtraces in
OpenBSD -> update it here as well so OpenBSD Rust code can produce
proper backtraces.

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust