- src links/redirects to extern fn from another crate had an extra '/'.
- src links to `pub use` of a crate module had an extra '/'.
- src links to renamed reexports from another crate used the new name
  for the link but should use the original name.

This is mostly just a documentation fix as I don't think stability
attributes have any effect on macros.

Implement Binary, Octal, LowerHex and UpperHex for Wrapping<T>

Fixes: rust-lang#33659

Fix overflow error in thread::sleep

Fixes rust-lang#34330

I added a test to have a more clear error inside the function. Since `time_t` is `i64` and we expect `u64`, maybe we should changed the awaited type?

Add regression test for rust-lang#23281

Closes rust-lang#23281

…r=brson

configure: Remove clang version checks

We no C++ and an incredibly small amount of C code as part of the build, so
there's not really much need for us to strictly check the version of compilers
as we're not really stressing anything. LLVM is a pretty huge chunk of C++ but
it should be the responsibility of LLVM to ensure that it can build with a
particular clang/gcc version, not ours (as this logic changes over time).

These version checks seem to basically just by us a regular stream of PRs every
six weeks or so when a new version is releases, so they're not really buying us
much. As a result, remove them and we can add then back piecemeal perhaps as a
blacklist if we really need to.

…r=eddyb

don't warn on casting byte strs to slices

r? @durka

Mark concat_idents! unstable

This is mostly just a documentation fix as I don't think stability
attributes have any effect on macros.

[before](https://doc.rust-lang.org/nightly/std/macro.concat_idents!.html) [after](https://ollie27.github.io/rust_doc_test/std/macro.concat_idents!.html)