"is greater or equal to". Beside common sense.

library/backtrace also declares a feature called `gimli-symbolize` which
appear used, but the feature in std with the same name is unused, so
remove it.

io safety: update Unix explanation to use `Arc`

Fixes rust-lang#124384

Cc `@jsgf`

…s, r=Amanieu

String.truncate comment microfix (greater or equal)

String.truncate calls Vec.truncate, in turn, and that states "is greater or equal to". Beside common sense.

…kingjubilee

library/std: Remove unused `gimli-symbolize` feature

library/backtrace also declares a feature called `gimli-symbolize` which appear used, but the feature in std with the same name is unused, so remove it.