This increases consistency with other common data structures.

rust-lang#60532

This was removed in 8a7dded, but since rust-lang#62286 hasn't yet made it into
beta, this is breaking the build with llvm-libunwind feature enabled.

Furthemore, restrict the link attribute to Fuchsia and Linux, matching
the logic in build.rs since llvm-libunwind feature isn't yet supported
on other systems.

rust-lang#60532

Implement Option::contains and Result::contains

This increases consistency with other common data structures.

Document `while` keyword

This is a rework of rust-lang#60761.
Closes rust-lang#60736

r? @dtolnay

…_compiler_messages_p2, r=Centril

Normalize use of backticks in compiler messages p2

normalize use of backticks in compiler messages for librustc_typecheck

rust-lang#60532

Re-add bootstrap attribute to libunwind for llvm-libunwind feature

This was removed in 8a7dded, but since rust-lang#62286 hasn't yet made it into
beta, this is breaking the build with llvm-libunwind feature enabled.

Furthemore, restrict the link attribute to Fuchsia and Linux, matching
the logic in build.rs since llvm-libunwind feature isn't yet supported
on other systems.

…_compiler_messages_p3, r=Centril

normalize use of backticks for compiler messages in librustc_codegen

rust-lang#60532